Computers- nice, and you'll probably end up with one, but you don't
need them. I've had a bunch over the years, SRM, garmin, cateye, etc.
Right now, I don't even use a computer? Why? All the batteries are dead and I'm too lazy to replace them. Secondly, it's more fun for me to ride without all the data. So there
That's not to say they are bad though-
They can be handy in training- for example- it's nice to know/track how far you went, how fast you are going, etc.
Of all the features I've had, power(edit- power combined with hr) has been the most useful for SERIOUS training, but, you don't really need that for a 150km ride.
Average speed is fun too, but there are a lot of things that can throw average speed off. It's like the average speed feature on cars. I'll do a road trip and know I was doing 70-80 the whole way, yet get an average speed readout of "35mph" why? It's taking into account all the stop and go traffic lights/ piss/ coffee breaks/ etc. Even if you only take an ave. speed on a segment, it's still a little biased. Headwind? Tailwind? All the big guns were having a hammerfest that evening and you got a good paceline going? They will all effect ave. speed.
A lot of these fancy new watches do the same as the bike computers do. Garmins are neat because they can track your ride and show elevation, etc.
Calorie features are nice because they can estimate cal burning- but in my experience, a lot of them calculate high on on how many calories got burnt. After years of riding, you get a feel for what you are doing. When a 300 cal effort reads as 1200, you know something is off. I remember watching a "race across america" documentary. Some dude said he just burnt 12,000? calories by merely sitting at a rest station eating a banana. I don't think so. Whatever number he gave, he'd be dead due to burning more calories than he could ingest. Even if he sat there and ate cheesecake 24/7, he'd be dying (see cool tip #1 below).
The important thing about computers is to start collecting data for learning, but more importantly is computer coolness.
Cool tip #1.
Be cool. Do NOT announce your stats to other riders. Do NOT announce cadence on rides. Who f'n cares? 89 rpm vs 85? so what? Same goes for average speed, wattage, heart rate, etc. A lot of that stuff can be useful for personal understanding/growth, but to other riders is meaningless. Kind of like my 911 sc only has 180 hp, but it's almost a 1/2 ton (I'm guessing) lighter than my station wagon, which has over 200hp, but is heavier, so slower.
Announcing that stuff to the peleton drives me crazy. It is only permissible to announce 1.trip distance 2. elevation gain, only if someone ask. The quieter you remain, the cooler.
I would also get two computers, one for each bike. If I walked into a store tomorrow, I'd get two of the most simple computers out there. Get fancy garmin stuff/ powermeter info depending on your overall tech geek status, but keep the info to yourself for your own learning/training info. Apple watches and fit bits might be a good way to start if you already have them.
Whatever you get, make sure it has a way to display stuff so you can see it. Large numbers on the handlebar are nice. When your eyes are sweaty, or the computer is covered in rain, that's handy.
Also, don't get too hung up on tubeless vs. tubes. 40 years ago everyone showed up talking about gluing tubulars. With clinchers mtb everyone talks pinch flats. With tubeless, everyone talks about burping and not being able to get a good bead. Somebody somewhere is *****ing about something. These are the same people who are announcing about all their computer stats. For your purposes, I would only recommend that "if" you go tubeless, make sure to have some honest to goodness tubes in your pack. If things go south and it's raining. fixing tubeless can get daunting.
Good luck