Hoping I can get some tips here as a beginner.

Been playing about 3 months. Got about 18 chords down, most of the fretboard, some finger picking & strumming patterns, chunks of a few songs.

Still struggling with barre chords, quick chord changes (espec. to barre chords) & thumb position.

Where should I go from here?

Acoustic or electric? It's easier to learn on the latter, or at least a nylon string acoustic instead of a steel string IMO. Fast transitions between chords is something that only comes with a lot of practice and repetition, starting as slow as you need to play everything cleanly and ramping up tempo slowly over time.

Keep working on the barre chords.     You will get better every day.    They will open up a lot more songs

Searchcaster