Running a custom kernel is probably the best way to get plenty of kernel panics, in particular when you're new to customizing the kernel and check off every option and module that you consider superfluous because you think it makes your computer use less memory and run faster.
follow the guides on the gentoo wiki, and you'll be in pretty good condition most likely. Really I didn't run into any problems, until I pretty aggressively started trying to cut out stuff. Eventually I would disable something rebuild, and not be able to boot. Unless you are doing that kind of stuff, you will probably be fine.
So if I had two drives and 1 with windows installed and the other was completely fresh drive that I wanted to install linux on, for example mint Would grub be installed on the drive with windows efi partition?
If you get 2 drives, which is the only way I recommend dual booting. On the linux drive, just partition it like normal. So if you do a guid partition table. make the efi partition, and the root (or however you want to partition it), install grub. Do the normal grub setup, on that disk. then you just install os-prober, enable that in the grub config. the do sudo grub-mkconfig -o /boot/grub/grub.cfg and it will automatically detect other bootable drives and add them to the boot menu.
with that set up. you should be able to just set up the linux drive in the efi as the default drive to boot, or use efibootmgr and select it that way. And you can choose which os you want to boot from with that.
I have never dual booted with windows, so someone can correct me if it won't work like it does with other unix systems. But it works perfectly with multiple linux drives at least.
Sure but there are tons of them like that out there. Just the nature of the ecosystem.
Caveat services emptor Linuxbros!
I've literally never had a 2 minute boot with linux. The number of services hasn't even made a big difference in my boot times on linux. More than maybe at most a couple seconds if I have something a bit more complex set up. And a couple seconds is on the high side. Most of the time, the init system isn't even the longest part of booting. It's the bios, then the kernel (at least with the normal default precompiled kernels distros ship) that takes up most of the time. Then the init just fliest by. Because at least now days, most init systems are pretty heavily parallelized (except openrc by default, but you can change that).
The only thing I've had hang, was shutting down. Sometimes a program won't react properly to the signal it gets, and the system will wait about 90 seconds before sending it sigkill, if you don't change the defaults at least.
All that is to say. If you have your system taking 2 minutes to boot, you might want to look into what is going on. Because that isn't a normal linux thing.