I haven't seen recent recruiting program documents so it may have changed or I may be remembered incorrectly. From my recollection:
MDSSP is a 2:1 commitment during medical school (1 year of payback for every 6 months of stipend), payback starts post-training
STRAP is a 2:1 commitment during residency/fellowship, payback starts post-training
HPLRP is a set amount of repayment for every year you agree to serve after training
If you take MDSSP and then STRAP, your MDSSP obligation goes down to 1:1
If you take STRAP, for PGY-3 and on you can also take HPLRP
So 4 years of MDSSP, 3 year residency with STRAP, and 1 year of HPLRP taken as a PGY3 would give you 7 years of stipend and one loan repayment for a very rough total of ~$225K. If you join the Guard, you may have some state specific benefits. You'll also get ~$70k in military pay during that time. In exchange, you spend your 7 years of medical school in the military and then owe 4+6=10 years of service post training for a total of 17 years in the military. At which point you might as well finish out 3 more years, get your loans fully forgiven and get a small military retirement benefit when you hit retirement age.
It's not a terrible deal, just an insane deal to commit to upfront. It's crazy that you can end up being 40 telling your kid you have to miss their birthday or your significant other you can't go on vacation with them because when you were 22 you took some money from the government and now you have to go to Manchuria for 6 months.