Triathlete here, rather than cyclist. I also do 2 sets per week. Most of my S&C plan was developed with a physio after I had repeated glute/hamstring/back issues. Involved lots of heavy lifting. I’ve been pretty poor doing it over the last year. Mostly because I was having trouble with fatigue and completing workouts once I got a couple of weeks into it.
I’d been adding core and upper body strength to the program my Physio had devised. It ended up being way too much. So I cut it in half and do it over 2 days now. Session 1 is deadlift, single leg squat, single leg bridges, upper body pushes and some core work. Session 2 is squats with bands, single leg deadlifts, core work and pull ups. Each usually take 45-50 mins. I don’t have access to heavy weights with the Covid restrictions. The max load I have is 45kg at the min. But that has probably been beneficial this time - I’ve had to slow the progression down. Even at that the first 4 weeks of trying to integrate it into my training plan I was just bone tired in a way I just don’t get from endurance training. I’m 8 weeks in now and seeing real improvements - so it was worth the struggle.
The first session of the week I do on the same day as my hard run. I find that it doesn’t affect my running in the same way as my cycling. I’ve a rest (or active recovery) day the following day and then my hard bike workout the day later that. The other one coincides with an easy endurance/recovery spin. This time the day before a long run. Again doesn’t affect the run in the same way. And if I’m a bit tired on the run, no harm - you kind of have to get used to that anyway for races 
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Sorry for the length. There’s some great advice over on the Strength Training Forum, there’s a bit of reading to get through it though 
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