Sweet Spot, Threshold or VO2max? When to choose which?

I am cycling for 1.5 years now and want to get a little more serious this year. I am currently riding 3-5 times / week with 1-2 speed sessions and the rest basically zone 2 or occasionally group rides.

I am not quite sure, how to get the most out of my training. Should I do specific phases over the year or simply stick to what I’m doing right now? Do you mix Sweet Spot, Threshold and VO2max Workouts through the weeks or do you do them during specific phases of your structured plan for the year? When should I do which? I know roughly what the goal of the workouts is, but how do I decide what I need to train next?

I am not planning on doing road races but want to get faster for the group rides and want to be able to sustain a higher power for longer times. Maybe doing some longer gravel events later in the year. Also being able to ride faster and longer while bikepacking would be awesome.