Don't start an SMP until you're actually ready for med school. Any good SMP is going to put you through some of the first year of med school. Very intense, high stress audition. An SMP is a weak choice for a med school warmup, particularly with your stats.
Cert programs can be anything, and the cert doesn't matter at all. The program might be fine, it's just meaningless to have a certificate for it. One thing to worry about with a cert program is whether you're eligible for financial aid, because usually you have to be degree-seeking to get federal money.
As an example, EVMS has an SMP that has you sitting in med school classes with med students. Then there's VCU, which has a cert program aimed at MCAT prep and solidifying academics. Neither program has a strong linkage with the host med school, but a subset of students in these programs frequently get into the host med schools.
Don't get confident about the host MD school accepting you, unless you get into Temple ACMS or Tulane ACP. You should still apply early and broadly, preferably after you complete the program. You get no credit for being enrolled in such a program. And be very concerned about the cost of attendance at your target MD schools. Get instate public tuition if at all possible. It's entirely rational to freak out about the debt you'll have after med school.
You don't mention whether you've taken the MCAT or if you've applied to these programs yet. In any case, rigorous time-consuming MCAT prep and a top 20% score are what you need. (We don't know what a top 20% score is with the new MCAT yet.)
Best of luck to you.
