Hmmm. Pull-ups don't work to well for messes. I've had IBS for as long as I can remember and if you are looking for protection I recommend a diaper with a inner leak guard. Some of the better pull-ups do have leak guards. The problem with pull-ups in general is they, well, pull up and, if they get the least bit heavy, don't stay up. Molicare, Abena, Northshore and Tena make an intermediate diaper and I believe most of them have the inner leak guard. You can always add a pair of plastic, nylon or PUL pants over the diaper that will help contain an accident until you can get changed.
I gravitate toward the most premium diaper I can afford due to my OAB and IBS, but there are times I really want a lighter version so I know what you are trying to find. The problem I have with this search is that when you find that lighter diaper and start wearing it, if you are the least bit IC, you inevitably run into situations when you wish you had more protection than you do. Been there and done that.
I am IC at this point bladder only but do also have IBS and my light diaper is nothing below the level off a Northshore, anything less seems to me can leave you in the bathroom asking what now ? That's not a position I ever want to be in.
Having IBS myself, I'd recommend diapers over Pull-ups for this condition for many reasons.
You are going to want a heavy duty premium diaper for your own sanity when it comes to overall protection, odor control, and anything else you can think of. Pull-ups are hard to change from one to another in public, so if you want to be pee in the toilet, you can always slip them down. With premium diapers, usually there are two level tabs that can be adjusted if you ruin the seal.
My mindset when having a flare up is to switch to diapers entirely for the duration. Because of my O.A.B. & mixed incontinence (Still have control, but I leak throughout the day and need to pee constantly), I choose this as a time for piece of mind with wearing diapers, and I do not tamper with the seal or bother using the toilet to urinate. I will always try to make it to the toilet for #2.
I can't add anymore than an endorsement to what has been said - I once used pull up - and only once - I was fine with urine but hen came the IBS explosion and the - well to put it Bluntly - messy legs and a very funny waddle to the nearest toilet - never again
Pull ups are meant for people who have moderate incontinence issues. They are designed to be used during an entire work day. They are able to be pulled down so the wearer can go when they can. They are usually made with little to no leak guards. If they do, they are pretty useless for your situation. The crotch is narrow, no leak guards, no leg cuffs.
They do have products designed for IBS out there, depending on your need, there's different levels of products.
If it's bad, you'd need a full diaper with leak guards. Not necessarily padded thick (unless urinary problems are present) are needed, a thinner diaper with the right features would suit you well.