Root, root n 5th, walking are, sort of, processes rather than categories and not locked into particular genres when one listens closely.
Stu Cook of Creedence did a lot of root n 5th and often, like many country players, did octave of the root & 5th so that the 5th was the lower note, (also very easy to play as the 5th is a string above the higher root and in the same fret),... simple but it's what works for the song.

Nick Lowe has excellent melodic sense and is careful to not clutter his pop melodies with his brilliant basher bass parts.

I start on the root when planning a bass track, THEN I try to fit in the rest of the chord when & where I can as a walk/run/riff BUT it depends on the song, the ease of execution and the time to move about. I've been aware - and try to keep an eye/ear out - to avoid playing the 3rd when the melody (particularly a vocal), is singing the 3rd...it seems to clash.

If you get a chance to listen to Budgie's version of Baby Please Don't Go you'll hear the bass part change for section of the song but in the main riff it moves to walks, runs and fills as the song progresses across five and a half minutes. A gruelling song to sit on that main riff but Bourke keeps his focus with subtle change while retaining the drive and groove.

Last edited by rayc; 3 hours ago.
Cheers
rayc
"What's so funny about peace, love & understanding?" - N.Lowe