FPS's can be very taxing to record, without a doubt - even more so on a laptop.
I mean, sure, you can turn down all your settings to the point that everything runs buttery smooth, but then the problem is that you have probably turned them down so much, that the audience will be turned off by the 720p, 30fps recording... The FPS scene in particular is quite demanding when it comes to recordings and streams, in my personal experience.
When you say walkthrough genre, what do you mean precisely? I'm asking because, to me, FPS's and the word "walkthrough" don't have that much in common. :-) For example, are you talking about guides for CS:GO or a walkthrough for Borderlands 3?