I'm headed to SW Michigan in a month.

What are the current rules for businesses, restaurants, etc?

Masks?  Quarantine? Do people give a shit?  Are Police or Health Dept officials lurking around every corner?

Thanks!

Masks required for businesses. Compliance and enforcement varies. Capacity limits for restaurants. Some are requiring that you leave your contact information if you are dining in for contact tracing. Lot's of karens around, but it will vary a lot depending on where you are. Police won't bother you unless they have to. If you go without a mask to a store and they tell you to leave, just leave, don't argue. Cops won't be happy having to show up to that shit and they will hit your ass with trespassing for wasting their time.

It depends.

The edict is still in place, and the Marxist whore sends her DOH Brown shirts out to screw over businesses, that don't comply.

Several County's are re-routing the "No Mask" complaints to the AG's office, and wont enforce.
Many of the larger city's on the other hand, are enforcing the Edict due to so many authoritarian boot licking FIB transplants.
Hotels are open, Restaurants are at 50% capacity. No mask needed outdoors.

If it's a small, grubby, Farm town, nobody gives a shit except for restaurants.

The Zoo, Holland,Muskegon, Mattawan, St.Joe, and the beach towns, are libtard shit holes, so mind the mask to keep the Karens from screeching.
Same with anyplace that caters to FIB's.

Where in SW Mich are you heading?

Headed to Muskegon for some work.

Last time I was there, I remembered as a very nice place, and good people. I’m really curious what the vibe is like these days. I know Muskegon skews somewhat liberal, but there are significant conservative areas outside of the city center. I just don’t want to be disappointed by driving into a sea of  zombies and Karen’s. Have people completely forgotten what freedom looks like?

One thing just to be aware of is that some restaurants are following corporate policies, I think, and may still not be open for dining in. It seems to be mostly the big chain fast food places, like McDonalds. Some places are allowing customers to walk in and order food to go, and some are still drive-through or curbside pickup only. So although Michigan is open for 50% capacity indoor dining, some individual restaurants aren't doing that. There's no real pattern to it. Panda Express is carry-out only, Panera is open for 50% dining in, as two random examples. Local (non-chain) restaurants are of course all open for dining in (and hopefully will weather all of this). I just wanted to mention that in case you're out driving around and want to stop in to grab something to eat and sit down.

There are some nice spots in Muskegon , by the lake. Most folks won't go there. I'm 40 miles NE from Muskegon, by the Muskegon River

Similar question as I'll be headed to Ann Arbor in June, so I appreciate the local intel.

I've checked reciprocity between MI and my state (CO) and it looks good to go in terms of concealed carry. That said, I'd be flying in/out of Detroit. Any issues specific to that city or the airport with regard to traveling or driving or possession of handguns?

What I see on the net indicates that my CCW permit is valid and recognized by MI so it seems as though all I need to do is follow the TSA rules getting in and out of DTW.

Thanks for any information or links to definitive sources.

Follow TSA rules. Michigan has preemption. You do have to inform police you are carrying if stopped by them though. Not sure if CO has that law.

Sounds like you have the CCW info and should be good to go following TSA rules, and if are stopped you have duty to inform (already stated).  The airport is the "Detroit" airport even though it is about half way between Detroit and Ann Arbor.  Be forewarned that Ann Arbor is an incredibly liberal city and you will most likely run into mask Nazis and such.  There are still plenty of cool things to see there and good food.

There are some CCW restricted premises that are worth noting (included in links).

Some links that might be helpful: https://www.tsa.gov/travel/transporting-firearms-and-ammunition

https://www.michigan.gov/msp/0,4643,7-123-1878_1591_3503_4654-10947--,00.html