I went through the exact same rabbit hole last year when I built a hidden bar shelf that lifts out of a cabinet. I wasted a week on random actuators from Amazon until I figured out what actually matters—stroke length, force, and speed are the big three, but also watch the duty cycle if it’s going to be used frequently.
For your monitor, a 12 volt linear actuator with around 150-200 lbs force (you want more than you think, for smooth motion and stability) and something like a 6-8 inch stroke would probably work fine (12v linear actuator). I ended up getting mine from Progressive Automations—they’ve got a really good selection and detailed specs, which helped me narrow it down without guesswork. Also, their customer support actually helped me pick the right model, which I can’t say for most places. Just don’t go for the fastest option—they tend to jerk a bit unless you use a controller with speed adjustment.