Use whatever dedicated VGA switching gear, or KVM (Keyboard, Video & Mouse) solution you feel that is appropriate for yourself. In my pre-purchase research, I read that some work better than others. I got lucky on my 1st purchase, and have no issues. For my own current needs, the one I bought works well, and gives me future options for expandability.
They also make Dual-Display KVM switches you know, in case you have a need for that. I personally didn’t want to spend the extra cash for that option, which almost doubles the price, and would have just been a future option, that I may or may not use anyway.
You may also want to consider, or reconsider how you use your 3 screens with 2 computers (as I do too)…there’s always more than one option 
For me, since I had been using 3 screens on my one main DAW, and was basically using that 3rd screen just for placing all my VSTi windows on, it was only a natural transition to have the 3rd screen on my dedicated VSTi machine. This of course makes my 4-port KVM switch totally over-kill for now, but as I said, it gives me future expansion. Currently, the way I use them…I don’t even ‘need’ to connect any of my screens to my KVM switch at all, as I really only need to switch my keyboard & mouse. I could have very well just bought a keyboard & mouse switching unit for the time being, but at the time I bought it, I had the intentions of adding more machines.