The below summary is from the National Immigration Law Center, and is the best summary I've seen so far explaining the current rule vs new rule on Public Charge Policy:

On August 14, 2019, the Department of Homeland Security (DHS) published a final rule related to public charge in the Federal Register. According to DHS, the rule will not take effect until October 15, 2019. [The rule will not affect cases filed prior to October 15, 2019].

This new rule will mainly impact those seeking permanent resident status through family member petitions. The rule will not take effect until mid-October 2019. Until that time, all pending adjustment of status cases and those that are postmarked before October 15, 2019 will be adjudicated under current standards.

Additionally, many organizations have indicated they will file lawsuits challenging the legality of the rule. Thus, even after publication, legal challenges could delay implementation.

Here are a few important points regarding the public charge rule:

 The new rule interprets a provision of the Immigration and Nationality Act (INA) pertaining to inadmissibility. The inadmissibility ground at issue says a person is inadmissible if they are likely to become a public charge. INA § 212(a)(4). This law only applies to individuals seeking admission into the United States or applying for adjustment of status. This provision of the law does not apply to all immigrants.

 Public charge and this rule do not apply in the naturalization process, through which lawful permanent residents apply to become U.S. citizens.

What is the current law?

 Currently, immigration officers decide public charge by evaluating whether an applicant for a green card or an individual seeking to enter the United States on certain visas is likely to become primarily dependent on the government for support. Primary dependence 
refers to reliance on cash-aid for income support or long-term care paid for by the government.

 To decide whether an individual is a public charge, immigration officers rely on multiple factors specified in the INA. They must also rely on the “affidavit of support,” which is a contract signed by the immigrant’s sponsor , indicating that the sponsor will financially support the immigrant. This affidavit of support offers strong evidence that the immigrant will not become primarily dependent on the government.

 Under existing policy, immigration officers also consider whether an immigrant applying for a green card or admission to the United States has used cash aid (such as TANF, also known as “welfare,” or SSI) or long-term institutionalized care in the past. Immigrants who have used this form of assistance will have to show that it is not likely they will need these resources for support in the future.

 Use of publicly-funded health care, nutrition, and housing programs are not currently considered negative factors for purposes of public charge. Beginning on October 15, 2019, the new rule will consider some of these benefits in the public charge determination. This is a drastic change from longstanding policy.

What’s in the new rule?

 While the test for whether someone is likely at any time to become a public charge will still be prospective as required by the statute, the new rule redefines the definition of a public charge. Now, instead of assessing whether an applicant is likely to become primarily dependent on the government for income support, the new rule defines a public charge as a person who receives any number of public benefits for more than an aggregate of 12 months over any 36-month period of time. Each benefit used counts toward the 12-month calculation. For instance, if an applicant receives two different benefits in one month, that counts as two-months’ use of benefits.

 The rule expands the list of publicly-funded programs that immigration officers may consider when deciding whether someone is likely to become a public charge. Under the new rule, Medicaid, the Supplemental Nutrition Assistance Program (SNAP, formerly known as Food Stamps), Section 8 housing assistance and federally subsidized housing will be used as evidence that a green card or visa applicant is inadmissible under the public charge ground.

 The proposal also considers that all use of cash aid, including not just TANF and SSI but also any state or local cash assistance program, could make an individual inadmissible under the public charge ground.

 Benefits received by family members of the immigrant will still not be considered in the public charge determination. Additionally, Medicaid received by applicants while under age 21 or while pregnant are not considered. In addition, the proposal does not change long-standing policies that allow immigrants to access emergency medical care and disaster relief without public charge repercussions.

 It is important to remember that prior receipt of benefits is only one factor in the public charge test. The new rule sets out criteria for considering several factors in assessing the likelihood that a person will need more than 12 months of public benefits in aggregate over a 36-month period in the future. The rule also elaborates on criteria for considering financial status, size of family, age, education, skills and employment, among others.

 The rule allows immigration officers to consider English proficiency (positive), or lack of English proficiency (negative); medical conditions and availability of private health insurance; and past use of immigration fee waivers. The rule will require immigrants to attach a Declaration of Self-Sufficiency when applying for a green card in addition to the many forms already required.

 The rule creates “heavily weighted negative factors” and a couple “heavily weighted positive factors.” It is a heavily-weighted negative factor to receive more than 12 months of public benefits in the aggregate over the 36-month period of time before submitting the application for adjustment or admission. Heavily weighted positive factors include having a household income of at least 250% of the federal poverty level. It is not clear how an officer should decide a case that has a heavily weighted factor or both heavily weighted negative and positive factors.

 Bonds are possible where an immigration officer finds inadmissibility based on public charge. Bonds will be highly discretionary and the new rule says that some factors that will generally make an applicant ineligible for a bond.

This new rule, if implemented, will mainly impact those seeking permanent resident status through family member petitions. Immigrants should consult with an immigration expert who understands public charge to learn whether the public charge rule even applies to them or their family. Remember, many categories of immigrants are exempt from public charge. The rule will not take effect until mid-October. Until that time, all pending adjustment of status cases and those that are postmarked before October 15, 2019 will be adjudicated under current standards.

Existing policy is still in effect. The new rule will apply to adjustment of status applications postmarked on or after October 15, 2019 . The new rule will not apply to adjustment of status applications that are pending or postmarked before that date. Additionally, legal challenges may delay implementation.