Company getting acquired, what to expect?

Expect working conditions to keep getting worse until you decide to leave (no matter what the CEO or management claim to you, they got their payday, they don't give a shit anymore, they're almost all getting out as soon as they can).

Raises and promotions will likely freeze, benefits will likely change and become worse (at least I've never seen them get better from a merge), you're probably just going to get stuck where you're at, if you were a permanent employee at least. People will steadily leave, and the company will probably try to just dump their responsibilities on someone else, and be slow to hire replacements (if they do at all).

Considering you're a remote contractor, some of that might not apply to you directly, but you still might get more work dumped on you as other employees start leaving.

I don't know about options, I never worked for a company that had options that ever ended up being worth anything.

I've stayed way too long after a merger before, things never got better, even after several years, they just kept getting worse, and promises made to me kept getting broken. I won't make that mistake again.

Been through an acquisition on the other end.

My main piece of advice is to talk to the employees of the larger company to suss out whether they like the company culture, whether you can or want to work with them and the processes your company will inherit. Treat it as an unofficial low-stress way of interviewing a company. :)

It's pretty much a given rule that the culture of the smaller company is subsumed into the large one - the only question is how fast it happens.

trust no one. get it in writing. seriously, having been involved in several acquisitions, even the majority stakeholders may not completely know what is going to happen. The stakeholders may be told anything by the NewCo, simply to keep it together while the transition is under way. Acquisitions are not always good, or bad, but they never quite go exactly as presented. If you have ownership, stay sharp, keep your wits and remember that once the paperwork is completely signed it is no longer yours. And it is not a done deal until the money is in your bank account.

I was an EU based contractor in an US company which decided to sell.

It went downwards, the ugly heads of incompetent middle managers reared up, I went away. Most others also.

Expect Change - that is really all we can say. Every acquisition is different, many of them are painful (not all) but none of them leave things unchanged.

Expect the new owners/management to day don't worry, nothing will change, your job is safe, it will be just like before, only better.

... followed by everything changing, jobs being eliminated due to "synergies", a rapid process of keeping the best people who are aligned with the new direction/goals, eliminating those who are not aligned, and bringing in new people from outside.

The second things feel like the new owners don't want to improve conditions or help you make things better, run. That's the clear signal that your company was purchased to try and milk it, kill a competitor, or some other game that isn't "make the products better"

My own experience is that buyouts have all the uncertainties of a new employer (and more) and all the baggage of an old employer. If you look for new jobs seriously and the buy out looks like your best offer then it might be right to stay, but most people stay from inertia.

Impossible to tell and most likely no one in the company will have answers for a while - so get used to that.

It takes a long time to figure out details to a point where your questions can be answered, that's common in all acquisitions so don't despair.

Is it a merger or a subsidiary acquisition? In my experience these are wildly different things

Lawyer up, don't come here asking for legal advice.