It probably should also be pointed out that it is a lot easier to combine chords with melody lines when you transcribe the song to a key where the chords are more amenable to that style of picking. In particular, the keys of G, C, D and A, plus Em, Am, Dm, then E and Bm when you get more proficient, are the easiest to find the melody notes with since the first inversion chords tend to have open strings in them, which themselves make up some of the melody notes you need.

It’s not that difficult to adapt to playing songs in 3/4 time, but yes 4/4 songs are best suited to that style. However, some melodies just fit their chord sequences better than others, eg Streets of London compared to (struggling here) say Leaving on a Jet Plane, but you shouldn’t be afraid to try substitute chords or partial ones as mentioned above. Interestingly, rock guitarists and the like tend to belittle this style of playing, possibly because it relies on much use of the beginners’ cowboy chords, but ask them to actually play a recognisable tune, as opposed to a riff, and they often don’t know where to start.