lag question

first off, I am new to the G3. I bought on used (in mint condition) and it had 5.0.1 on it. I loaded all my settings and apps that I typically use and to me it worked great...No huge amounts of lag...it was actually. pretty smooth Well when I installed TWRP, it wouldnt boot...it would get security boot error (or something like that)

So then I had to restore to stock...which downgraded it to 4.4.2 and I set up all my stuff on kitkat because the day I downgraded, it wasnt seeing the OTA update. Well the next day the OTA finally came through for 5.0.1...so I took it and when it it got done installing, this time, there was noticeable lag. Mostly from opening the app drawer...opening every time was a stuttering mess...also alot of the times scrolling screens.

I have read this phone is notorious for lag...but my original use with 5.0.1 wasnt bad...it was only after I downgraded to kitkat and then took the OTA.

should I have took the OTA, then factory reset, and then set it up? Maybe having everything setup on 4.4.2 and then taking the OTA caused the lag?

any help would be apprecaited...and I dont want to switch launchers...I always like to use the one that comes stock with the brand of phone.

thanks for any and all help.