Prometheus and Arrival are set in the SAME Universe.

 The ships do look similar and I can sort of see the creature comparison. That is an interesting observation! 

Arrival and then Prometheus:

UNFORTUNATELY...... there is NO connection between the Movies.

Aesthetically the Ships are similar but up close they are also Quite Different.  I can see the reference made about the ALIEN from ARRIVAL and the Trilobite from Prometheus.....  however the Aliens in Arrival you dont really see them fully.

Here is the Concept Art by Carlos Huante for the Movie ARRIVAL

In the Movie we only get a Short Glimpse of them (Heptapods) Full Shot.

However....... here is where it could have been Interesting as far as Connected with Aesthetically Similar Alien Species but NOT in anyway actually Connected.

There was another Concept Work for one of the Alien Prequels that as similar to the Arrival Heptapods Concept but i cant seem to come across it.

But here is ONE of the Engineer (Whale) Concepts for Prometheus.

You can Slightly see some resemblance to the Heptapods from Arrival.

Here are some other Heptapod Concepts that are Similar to some of the Neomorph Concepts for Alien Covenant but also Trilobite for Prometheus.

The TOP Concept for the Heptapod (3rd Image Above) is Very Very Similar to a Earlier Concept of a Spore/Face Hugger from Alien Engineers Draft (early Prometheus story)

EDIT...  Found the other Concept for Prometheus that i was on about that looks like the Aliens (Heptapod) in Arrival.

So depending on WHICH of the Concepts from the Alien Prequel and Arrival then we could have had TWO very similar looking Movies Aesthetically...

But that does not mean they are ever intended to be connected...  i think what my Reply does show is that some Ideas for the Alien Prequels could have given us something more Lovecraftian than we GOT or indeed what we had the the Original Franchise.

Interesting.

Dont get me Wrong, i dont mean to Dampen the Ideas...

Aesthetically yes there are some similarities but thats where it STOPS....

What i was looking at with my previous reply is that there was UNUSED ideas and Concepts, that could have introduced us to things in the ALIEN Franchise that were VERY Alien looking, compared to the Exploration of the Engineers especially in terms of Alien Covenant.

If we look back at PROMETHEUS and we ignore the Deleted Scenes of the Elders...  then we dont really see the Occupants of the Teardrop/Pebble Ship.  We get the indication that this SHIP is what drops off the Engineer to perform his Sacrifice to Seed Life on a World...  but we dont see who is on the Ship....

More Engineers? (as Deleted Scene indicated) is the Ship Automated? or could we had Speculated that some other Race/Species is on the Ship that is FAR more Alien Looking and Lovecraftian?

Alien Covenant kind of reduces such Speculation but it does-not mean in Context to the ALIEN Franchise that something more Alien Looking could not be Introduced like what we saw in ARRIVAL....

But thats NOT to say the Franchises are or ever would be Connected.