No evidence of metastases is great! Now onto the business of curing this sucker! You are "high risk" because your PSA is over 20. Your PSA density is quite elevated. That calls for some extra measures.
The clinical trial (option 1) sounds good to me. Those are some very powerful hormonal agents, and you can't get apalutamide outside of a clinical trial. It looks especially attractive from my POV because they are only proposing them for 6 months, as opposed to 18 months with option #2. They are watching you closely and managing the side effects of the hormone therapy, and if you feel it is intolerable, you can quit that regimen at any time and go back to leuprolide only, so I don't really see much risk of that to you.
As for option 3: Take a look at MSK's nomogram on the efficacy of surgery in your case: GS 4+3, cT3a, and PSA of 20.44. As you see, there is a very high probability (77%) that you will progress and need salvage therapy soon afterwards. Salvage radiation compounds the side effects of treatment. On top of that, 75 yo men just don't recover very quickly from surgery - increased expectation of lasting incontinence./www.mskcc.org/nomograms/prostate/pre-op