today i run my axis after switching from 15% to 20%. During first two tanks it choked at quick start but after third tank it run perfectly. In the half tank glow plug broke. I changed for the new one - cold. Unfortunately it started to choke again. Is it normal and i should run few tanks to let it "feel" the new plug or sth is wrong?

anyway what would be the best plug for axis with 20% fuel? Cold, warm, hot or sth else?

and which for the gs21r also 20%?

thanks in advance

Try going back to factory settings and then tune from there. Changing nitro content often requires a different plug rating.

I don't have any experience with the engines you mentioned but depending on your outside temps you can try 5 or 6 rated plugs with 20 % nitro in .21 engines.
make sure the filament of your old plug didn't break and fall in the engine.