While CBD is an important cannabinoid for its medical usefulness, THC is just as good at fighting inflammation.
Indica, Sativa and Hybrid strains available today will usually all contain a lot of THC, but other cannabinoids such as CBC, CBG, CBN, CBD (and over 40 more different ones) will come in different ratios. It's that ratio that will impact the perceptual response to the strain, among other things.
The simplest answer is that any strain will effectively treat an IBD even if it has 0% CBD. So long THC is present, it will help. The presence of CBD makes it more efficient, but its absence does not make cannabis useless.
Because Sativa and Indica strains evolved in different climates, their cannabinoid profile also is different. Indica strains will induce a lot of lethargy and sleepiness that can be felt across the entire body depending on the ingestion method. Sativa strains on the other hand can produce the opposite effects: they induce feelings of general well being, a kind of uplifting aura. When you mix those strains to create hybrids, then the response will be a mixture of those side effects as well.
Cannabis users who are experienced and take it for medical purposes usually prefer to avoid the high during the day so they can get on with their work. That is why I prefer a Sativa dominant strain for day use, and an Indica dominant strain for my dose before bed.
If you have a choice, you should seek CBD rich strains regardless on whether it is indica or sativa. Which you prefer to use comes down to personal preference after that.
For tinctures or oils, I prefer to use indica strains. I find them more effective for those applications. For vaporizing, I will use both depending on time of day.