I also experienced the same issue with some lag in PvZ2, sometimes the lag is so harsh, it crashes my laptop and forces it to restart.
What my experience of not much getting lag is CLOSE ANY UNNECCESSARY PROGRAMS (e.g. Google, A video game your not playing for several hours)
There is a FPS counter in the settings of Bluestacks 5, very useful to tell if my game is freezing/lagging.
The reason I am playing PvZ2 in my laptop is because it feels better playing then my old phone because I got used to the gaming conditions of Roblox and Minecraft. The screen is much bigger that I can see the graphics properly meaning I will have good experience playing. I have good eyesight meaning I can read very tiny texts, but still I gonna use my laptop. My old phone is technically broken due to it's battery drainage from all the heavy storage kept in there for like 6 to 5 years. I was very good in my 2018 progress of my old phone as I beat Adventure Mode, Ancient Egypt plants almost level 9/10, Got ALOT of early Arena plants since 2019. I plan to save my PvZ2 phone progress aswell as my PvZ Heroes Progress, and maybe PvZ1... but the phone won't let me as it will run out of battery after 5 MINUTES. And finally I felt like a wanted to make new profile and start over from the beginning as I'm already very good at my phone progress and at the point that it's so easy.
And that is my long reason why I use Bluestacks 5 to play PvZ2, but I don't only play PvZ2 on Bluestacks 5, I play several games like it's sequels PvZ1 and PvZ Heroes.