Questions in Hollow Knight

So I got void heart before killing The Hollow Knight and I was wondering if I was still able to get the first ending or if I had to do it in a new save file

Anyone know a good way to farm Geo? I’ve done almost everything possible before Kingdom’s Edge besides getting the Vessel Fragment in Ancient Basin and upgrade the Fragile Charms. I’ll give a sticker to anyone that gives me a good method. Thanks!

Any charms I should use for vanilla radiance?

I'm tryna get the voidheart ending

I am trying 112% the game first try and i am stuck on the watcher knights, any charms or techniques for fighting them

(BTW already got the chandelier)

which is harder to beat?

Where do you think the knight stores geo