I also find that it can be helpful to check community news posts for the most popular mod packs (usually on their discord), as they do a pretty good job of announcing whether the mods they shove together work yet or not.
All that said, 1.6.x type updates, where they aren't incrementing the first or second number, usually don't break as many things. Personally, I'd just make a backup of your entire Stardew folder before you install the 1.6.9 update (and the latest SMAPI update, and any updates for your mods) and see how it goes. SMAPI will usually warn you in the console window at startup if it sees any mods it knows have broken. If shit's fucked, just restore your backup copy and try again in two weeks.