I would suggest sticking to official gear for your Chicago weddings. I tried a cheap third-party one once and it felt loose during a fast-paced ceremony, which was terrifying tbh. Make sure to get the Canon Mount Adapter EF-EOS R Standard if you want that weather sealing. Personally, i find the Canon Control Ring Mount Adapter EF-EOS R a bit fiddly and easy to bump by mistake while shooting...

A bit late to the party but I went through this exact same internal debate when I traded my 5D for the R series. I do a lot of event work and was super paranoid about my EF glass not performing. I ended up testing a few different routes because I hate the idea of a single point of failure during a big shoot.

• Canon Drop-In Filter Mount Adapter EF-EOS R with Variable ND Filter: This thing is a total lifesaver for outdoor ceremonies. Instead of fumbling with screw-on filters when the sun is blasting, you just slide the ND in. Technically, the glass quality inside is top-tier. I havent seen any weird color casts or loss in sharpness, which is a big win for those bright Chicago afternoon shoots.
• Viltrox EF-R2 Control Ring Mount Adapter: I picked this up as a budget alternative to see if the ring actually mattered. It works, and the AF is snappy enough, but the physical build feels a bit thinner. One thing I noticed is the internal flocking or the matte finish inside isnt as deep as the Canon ones. Basically, it feels okay for a second body, but i wouldnt rely on it as my main for a 12-hour day.
• Meike MK-EFTR-C Drop-in Filter Mount Adapter: This is a cheaper alternative to the Canon version. I tried it for a few weeks but the filter tray felt a little loose. It didnt give me that clunk of confidence that the weather sealing was actually doing its job during a drizzly outdoor session. From a technical side, the main difference is usually the internal coating. Cheaper adapters can sometimes cause internal reflections when youre shooting backlit subjects, which happens all the time at weddings. If youre doing high-end work, that extra coating on the official drop-in or high-end ones makes a huge difference.

Building on the earlier suggestion, i unfortunately have to agree that third-party units just aren't as good as expected when you're dealing with messy Chicago weather. I had issues with the weather sealing on cheaper brands where moisture actually seeped into the mount during a rainy outdoor shoot. It was a total nightmare tbh. Since you're doing weddings and need to save cash, here is what I found works best:

• Skip the control ring version entirely. I honestly found it kinda gimmicky and kept bumping my settings by mistake during fast-paced segments.
• If you really want to save, look at the Commlite CM-EF-EOS R Mount Adapter. It is budget-friendly but actually feels more solid than the Viltrox ones, though the sealing still isn't 100%.
• Another rugged option is the Fotodiox Pro Lens Mount Adapter EF to RF which is built like a tank for the price. Ngl, I ended up just buying a used official one from a gear exchange to get that peace of mind without the full retail price tag.

Gonna try this over the weekend. Will report back if it works!