Personally, I may just be an odd ball here, I find that there's no difference with my typing speed and accuracy with different keyboards, I currently have a mechanical keyboard for my desktop, but I see no difference between that and me using a bog standard keyboard, like a wireless one that I bought for £15 the other day, and that price also included a wireless mouse too, I bought them simply so I can use my desktop from the comfort of my bed, when it's hooked up to my TV, I just use them both for web browsing or watching films, not much else.
The mechanical keyboard is faster to type on once you get to use to the keypresses, and don't bottom out the keys with every press, or with the help of O-rings, I jumped from 80wpm to about 90 with a mechanical keyboard, but I don't think I'll ever buy mechanical again.
The keys on a thinkpad are just so nice to work with over the standard chiclet keys
Dont need a fancy gpu - all it will do is add heat and drain power. All you want is a good cpu, decent amount of ram and a nice storage solution - like a big ssd, and a nice keyboard.
Since you're installing your own OS there is no point in buying a new laptop that has say Windows 10 included. Just buy a nice HP, Dell, Lenovo 2nd hand & swap the hdd for a nice ssd. HP elitebooks and Lenovo thinkpads are bloody tough and perfect for lugging around campus, surviving falls etc.
A big SSD, in a laptop, that makes the cost go sky high, as an alternative, I was going to go for an SSHD, I mean that way I've got plenty of storage and I've also got a nice bit of speed when the computer boots.
I don't want to invest into something that's a silly price and as far as keyboards go, it doesn't matter as long as it works, for me. I'm able to work on all kinda of keyboards effectively, like with a mechanical keyboard, I'm sad to actually say this, but I don't see the big deal, I do a lot of typing, every day, a mechanical keyboard feels nicer and sounds nicer, sure, but for the price, I'm not sure I'd invest into anything fancy again and it's not like I have a cheap mechanical keyboard either, I have the Corsair K70.
I'll consider the Lenovo Thinkpads, as I don't KNOW if they have malware/adware/spyware on them, but I'm sure that the brand new one's do have all sorts of crap built into the firmware, but where could I get one from that I know it in a good condition, that's the only problem I have with buying an older/used/2nd hand laptop, I have no idea what the previous owner has done to it and I have no idea how reliable it will be.