Trouble deciding on structured training plan with weekend mtb ride

I’ve started doing structured training last year and made plenty of progress.

In march I stopped doing structured training and instead, started doing 100km commutes twice a week.
I also picked up mountainbiking, and ride my mtb every sunday (1-3 hours).

Now the days are getting shorter and I stop commuting on my road bike and want to get back to structured training.
I am having trouble deciding on a plan that works nicely with my sunday mtb ride on the trails.

  1. Last season I used the TR low volume polarized training plan.
    Would doing a 1-3 hour mtb ride in addition to the low volume polorized plan be a good idea?

plan would be as follows:
mon: (strength training)
tue: (polarized plan: low intensity) 1 hour
thu: (polarized plan: high intensity) 1 hour
fri: (strength training)
sat: (polarized plan: low intensity) 90min - 2 hour
sun: outside: mtb trail (1-3 hours)

I could also replace the high intensity workout from the plan, but I think the high intensity workout from the plan is more valuable than my mtb ride.

  1. I also consider going for a sweetspot training plan, but I find sweetspot training very hard right now ( harder than hard days on the polarized plan ).
    It seems my musclar endurance right now is pretty bad, riding at only 80% maxhr, my legs start burning after only a few minutes and can’t keep it up for very long.
  • Is sweetspot more suitable to help muscular endurance catch up with cardio vascular endurance?
  • Is sweetspott training something you need to get used to, to make it a bit more bearable? ( mental toughness and muscle addaptations? )