I've only bought two guitar online, both new. One from The Fret Shop in Huntsville on Reverb and another from Sweetwater. In both cases it went quite well.
I know not online but I have 4 within driving distance. Look online at what they have in stock--not all guitars listed--but I found my used guitar that way.
I've purchased all of my guitars either in-person at a local store/Guitar Center, on Reverb, or member-to-member sales on AGF and UU. I've also purchased parts from Warmoth and built my own electrics.
Looking at sound samples for particular models on YouTube will lead you to a lot of good guitar shops.