Blending in a guitar solo

I just do whatever sounds good for that particular song.There really isn't anything more to it than using your ears and doing what sounds good to you and is appropriate for the song.

There is no "right" or "wrong" and no such thing as "too loud".

I've heard very popular songs where solos were super loud, and others where they were buried in the mix.

If you are concerned with other guitars getting in the way, you can turn them down during the solo, or even take one or more of them out.  If you think of it as a live band with two guitar players doing rhythm parts during most of the song, whoever does the solo is going to have to stop playing rhythm during the solo parts... so, there is nothing wrong with muting some other guitar parts during the solo if you really need to in order to make space.