Just remember that the lagging etc. may not be on your end. If possible play and test at different times of the day.
Other thoughts:
First:
"right now the 5500xt is cheaper than the 570 for some reason "
How much cheaper? Be careful about counterfeit products.....
Second:
Take a careful, detailed look at the hardware and software requirements for the games that you are playing. Verify that what you have and what you are considering to buy are up to game requirements and hopefully even exceed those game requirements.
Third:
PSU.
https://www.tomshardware.com/reviews/best-psus,4229.html
Use the recommended power calculators.
Fourth:
Remember tracert and pathping. Again test at different times.
The reason/source for the lags may not be within your control.
Overall objective being to identify the source cause or reason for the performance problem.