I've been recording gameplay for a long time and I used to have many of the same issues you had. A friend introduced me to a software called "Snagit". It has a built-in editor and it is easy to trim and apply a few effects to your videos if you want to. It doesn't take up too much memory, and I've accidentally left it running for 30 hours at a time and it takes no more than 2 minutes to process that much film.
It does cost money, but the free trial lets you keep renewing it a few times to get up to a year and a half of free usage, and just google "Snagit cracked code" and it's easy to find codes for PAID snagit.
I've been using a cracked code for about a year now and snagit is by far the best recording choice if you want something simple.
Hope I helped someone at least
(P.S., you need to make your Arma display settings on "Fullscreen Window" instead of "Fullscreen" if you want Snagit to record it, otherwise it'll just record your desktop.)
