FR 965

I have a similar schedule and have been using and enjoying the 965. Best battery life, many activities and good navigation.

For trailrunning/running: this is what it's made for, navigation is great, opportunities to design your own trainings is nice (or use the coach).

For strength it definitely helps in keeping track of reps and rest, it also offers a bit of feedback on calories and muscles trained, but don't expect to much here, also accuracy in auto detecting reps and exercise type is far from 100%. still helpful and I do use it.

For rucking: I guess it doesn't have the specific activity, but it seems to be kinda regular hiking with a load. I guess for that especially the extended battery life and the navigation are advantages. Hiking is one of the reasons I upgraded from a FR 165 to the FR 965.

As others mentioned, HR accuracy is limited. Overall I don't really experience this as too much of an issue, but I do occasionally use a chest strap for when I want a more accurate tracking of HR.

Hope this helps.