I've got two physically different drives. Can't say I've ever installed two OS's on the same disk.
My Linux system can modify my windows drive without any problems, but my windows OS can't even see my Linux drive. I'm thinking that this might be because windows can't read ext4 formatting.
If you use two physically separate drives, you can set boot order in your bios, so it's like having two completely different machines. Over the years I boot to windows less and less, only really keeping it around for FPS games that need anti-cheat software, and for VR stuff.
This is awesome. I'm looking at all the stuff my VPN mates are downloading and they have good taste.