Most anti-virus companies share the same virus definition databases. The different scanners are 99% identical. There is little benefit to running many different ones on the same machine. I recommend you use an anti-virus that has some kind of real-time scanning and doesn't put significant loads on your computer or compromise your privacy by sending significant amounts of data back to the publisher. The Windows defender built into Windows 10 is probably the best really as its extremely lightweight and has real-time scanning. In any case anti-virus protection is reactive rather than proactive, keeping your software up-to-date and not clicking on suspicious links or downloading suspicious files is much more important than an anti-virus.

About your question of on-screen keyboard. That may work against some fairly basic keyloggers, but absolutely will not against more advanced ones. The main thing is to try avoid getting infected with a keylogger in the first place by practicing good security practices. Once your machine is infected then you are kind of screwed as the malware could potentially do anything you can think of and may be almost impossible to detect or remove.