When I looked for information on this border crossing this was the most relevant result that Google returned. Not sure if that was because of my locale. Now that I went through I feel free to update this otherwise older post.

I crossed the border on a monday morning and it was not busy at all, there were two other cars in front of me.

I was not asked for "presents", the baggage was not searched and "tourist/holiday" was a good enough explanation for the ukrainian official. No one else had any specific question for me elsewise.

In Odessa I heard reports that at the crossing from Moldova into Ukraine going to Bohlrad a "pResent" was asked for "I want to dRink coffee!" About 1 Euro was enough to satisfy his request.

Leaving Galati at 8:15 saw me in Reni with cash from one of the three or four ATMs at the main square. So that says something about the speedy process I think.

Both crossings were quickly done and 100% correctly executed by those involved.

The roads in Reni were incredibly bad, but by no means that should stop anyone from going the smaller road:

The road from Reni to Izmail was a pleasure to cycle on, probably 2 years old. The road M15 up to Kyrnychky was also good. There was hardly any traffic on an afternoon till Tatarbunary. The gas station had a room for 250 and nice food.

Until Zatoka via Kurortne the road was 98% in "fast" shape. Halfway between Tatarbunary and Mykolaivja the road was so bad for cars that they have created a secondary dirt road right besides the asphalt road. This leaves the asphalt road traffic free and at any time I could cycle a "clear path" between the potholes without slowing down.
The only bad part was through some frequently flooded "valley".

From Zatoka towards Odessa via the bridge the traffic got denser but only from Velykodolynske it was metropolitan.

I took pictures from most parts and uploaded them at https://www.crazyguyonabike.com/doc/page/?o=Ha&page_id=344751&v=1a

From Galati to Odessa 95% were good as a cyclist can wish.

The cliff at Kurortne was a treat. Much better than dreaming of a beach in Odessa only to find bad traffic in the way to the shore.

In Izmail a former functionary's hotel has been reported for less than 10€.

The border crossing at Isaccea has been reported to exist, with a day's notice in advance and for 250€ (officially, no bribery) to the ukrainian custom office -- as it is not a regular crossing.