>>2038238Your first question is really; is the frame suspension corrected and how much travel will it accommodate. That will determine if you can even use a suspension fork and what ones you can use.
The 2nd question is use case. Your comment about suspension eating your power is kind of true, if you don't lock out the front suspension it's absorbing some of your forward momentum. However if you are riding surfaces that you want suspension for then that's a no brainer. If you are riding reasonably easy gravel roads, dirt paths, rail trail, and pavement then I wouldn't bother with suspension because you'd rarely if ever see a benefit. If those are the surfaces you plan to ride with it, you will do fine as long as you can fit decently wide tires. The bike components are a tool, match the tool to the job. If you don't need or want to ride rougher surface, I wouldn't bother with suspension.
If you actually care about going fast on gravel, this would not really be a question at all and likely you are already barking up the wrong tree using an MTB frame unless the goal is effectively a drop bar MTB.
