Can TandemFit build me a race plan?
Yes. Pick 5K, 10K, half, marathon or your own distance, then either give it your race date or give it a target time and let it work out when you'd be ready.
How does it predict my race time?
From the runs you've logged, updated as you train, with a confidence rating attached so you know how much weight to put on it.
Does it work with my watch?
Apple Watch and Wear OS both have a real app: start, lap, pause and finish from the wrist, with the phone catching up afterwards.
Can I still lift while training for a race?
That's the point. The strength work and the running are in one history and one week, and difficulty is tracked separately per discipline so neither one distorts the other.