Yes overnight and get into the gardens as soon as they open. Might not be as bad post Covid but the place was packed by 10.30am as the coaches start piling in. Maybe a late visit might be better, perhaps someone has done it.
Yes as said stay overnight, I was there last month ,watch where your sat nav takes you i ended up in the village which would have been a pain if people were exiting or queuing for the gardens . Also pay online for your ticket online ,loads of websites though ,i will find the link i used .