When we talk about “strength”, we’re usually referring to neuromuscular capabilities, or how well you can activate the available muscle mass. This sort of work targets strength gains without increases in fiber diameter and increased body weight, and the rep range is very low, usually 3-5. Then when you’re chasing hypertrophy, i.e., bigger muscle fibers with greater cross-sectional area, that’s usually done in that 8-15 repetition range pushed to failure or very near to it.
As far as scheduling your strength workouts so as not to negatively impact your endurance training, our recommendation is to separate them as much as possible but do them in the same day rather than schedule strength work on a recovery day. This allows the cell signaling the least interference, your muscles the best chance at reaping both strength and endurance benefits concurrently, and your body the opportunity to fully recover between hard workouts. And it’s prudent to recognize that the best endurance athletes will never be amongst the best strength athletes and vice versa.
You could get away with strength work on recovery days if you stayed closer to the “lift heavy” philosophy and that 3-5 rep range though. As always, there’s some “suck it and see”, trial & error experimentation to be done, but avoiding carryover fatigue and confused genetic signaling is best achieved when you start your day with endurance and end it with strength (or do it the other way around) remaining mindful of how each workout type influences your sleep, aka, repair/adaptation.