I am on my fourth ileostomy. Probably up to about
4 years total with ileostomies. And I wear tight stuff ALL the time. I think all that matters is that you are comfortable on that day. Simple as that. Target does have "spanx like" stuff. I just saw it the other day there. Sorry but I don't recall what name they used on them.
Why don't you put on your your stocking/panty things that you used to wear and try them out around the house for several hours. See what you think. You may be a bit more comfortable going up a size because you have appliance stuff now.
But honestly.. I have never ever had any problem wearing anything too tight. I like tight things.. because it keeps the bag and stuff very secure. And thats how I dressed pre-ostomy so no reason I can't dress like that now.
good luck