I haven't encountered any problems with OpenOffice's word processor, but I haven't given its spreadsheet much of a workout since upgrading to Mojave. I've had to put a few pretty complex documents together and it works great.
For that matter, Mojave has been the greatest macOS upgrade to ever come down the pike. It's fast, it's stable, has great features and is really easy on the eyes with the across-the-board dark mode. Best of all, I can still use all of my Adobe Creative Suite software! I keep waiting for "the other shoe to drop," and so far, I'm one happy camper.
I avoided High Sierra like the plague after trying it out for a couple of weeks on my MBP. It made that machine crawl like an old PowerBook 5300 and just wasn't as stable as Sierra 10.12.x. Much of my Adobe software didn't run well at all under HS and half the features in Photoshop and Illustrator either wouldn't load or would crash the entire system under HS, even after reinstalling it with SIP disabled. And, yes, I had to reinstall it again after upgrading to Mojave, and had to do so with SIP turned off, but all of the tools, brushes, palettes, etc., work better now than even under much older macOS versions, even the third party add-ons.