You can remove perfmod by reflashing Streakdroid without the perfmod option in the install.txt file. Nandroid backups are on the external SD card (rom-backup file). You can resotre them via Streakmod recovery. The size will depend on what you have installed. Mine are between 500-800 MB. If you back-up a clean install it will likely be less. No sure what would happen if you ran out of room, either it wouldn't start or not be able to complete. I have yet to hear of any internal SD cards being damaged by perfmod, but have heard that some instability with certin programs. I have had no problems.
I did a full a full backup with nandroid..
I have not noticed any problem with the prefmod. I will not remove...
(everything work, no FC / Random reboot / or any problems)
But If there is something wrong , i can recover the current system now...
I just changed my build.prop, now works almost all gameloft games.
Thanks again! Helped a lot!