Install questions

I want to install Mint on my laptop and make it duel boot system with Windows 10. I started the installer and had a few questions so I stopped for now. The first is asked if I wanted to install alongside Windows Boot manager. I assume this means that it won't erase Windows? Next it waked if I wanted to install third part apps for media,WiFi..and if I wanted to turn off the Secure Boot Manager. What exactly does the Secure Boot Manager do??And does it off change the BIOS and/or boot manager and how does that affect my computer? I read that the Secure Boot Manager is "Microsoft way of keeping you from installing other OS's". Is that true? And I have my HD partitioned in three drives. It's 500 gigs. C Drive has 198 gigs-B Drive has 75 gigs and I use as my secondary drive for Windows. And I created a third E Drive to put Linux on. The installer did not show all the drives or letters to let me select the one I wanted to install on. It showed a drive with 200 gigs so I assume it was the drive I wanted. I assume the installer can detect the drive that has the Windows OS on it? And is there a way to see all the drives on the computer in the installer and chose the drive you want? Sorry this was so long but I want to get it right. Thanks