I think it really depends how you ask it. If the question comes off as "I'm thinking of doing [xyz]; what do you think?", the risk is that it will turn out being quite opinion based. On the other hand, it could also turn out being too broad if your question were just to be something along the lines of "I want to program in Ada; what board should I use?", even if there was a sideline remark that this is for use with IoT.
The reason that a lot of coding and/or hardware recommendation questions get closed as off-topic is frequently just that; the use of the product for IoT is superfluous to the nature of the question; if you replaced the word IoT with web serving, data management or some other technical field, the question would have the same value to future users. Such questions should probably rather be asked on Super User or hardware recommendations. It should be clear from any question how the issue / question / need / whatever arises from the project being IoT. In other words, IoT can't be something that you tack on the end of an off-topic general computer or networking question in an effort to make the question "ok."
For myself, if the purpose for the board being for IoT is of a great enough significance that it is important for answerers to know in order to answer the question well, then it's almost definitely on topic. Just make sure you include sufficient detail for answers to be concretely right or wrong, and clarify specific requirements that you're looking for in your hardware. Ensure that your question demonstrates clearly how it relates to IoT, and make certain that it does not solicit discussion, but seeks for a concrete answer.
To be honest, I feel like I'm kind of preaching to the choir, since you being an experienced user, I feel certain that at least 90% of this was already running through your head... 😃 But honestly, those are basically the things that I would recommend keeping in mind.