Community or species only 45 gallon

[ZanaZoola14]

Hello, I've managed to source a 45-gallon tank to be the last tank on my breeding rack (others are 35, so this is the bottom tank). I wasn't originally aiming for a tank like this; however, I came across this tank with a tight-fitting lid and working lights for a low price and grabbed it while I could.

Measurements:
Inches - 39x15.5x17.9
cm - 99x39x45

The original intention, back when I thought I was getting a 30 or 35-gallon, was shell dwellers. I am still interested in this, but with it being a larger tank, I am curious about what else would be possible within this tank.

My tap is hard water, about 12dGh, but it seems to be getting harder with a recent test coming out at 16dGh. I would also be more than interested in hardening the water. If needed, I will also do RO water as every other tank is a RO discus mineral water, so I will increase and mineralise to what is required.

(Today's reading from the tap - tested with a ntlab multi-test kit.
Ph - about 7.9, so it could do with being higher.
Gh - 20dGH or 356ppm
Kh - 9dKH or 160.2ppm)
It seems my water is hardening. Someone near me, in a different town (but likely the same supplier), had a Gh of 28dGh, so all the chance it will increase to that.

I am curious as to what others would do in a tank this size and dimensions. It also has a nice fitted lid, my only tank that has a nice fitting lid. I am interested in trying larger fish; I never really got the opportunity to with the size tanks I have.

I want to try something different, and for that, I am not sure.
I could always do the shell dwellers, possibly with some Julies, and make it a colourful semi-aggressive community. Or something else. (I don't mind doing species-only tanks).

In my head, I currently have it planned out into an x-y-z. With x being a side of shells, y being a side of rocks and caves, and z being the top-middle of the tank, mostly open water. It would only be one species of fish per type.
I am also thinking about building a slate wall to either go fully or partially across the tank's back wall. (the background will likely be a blue colour in case I go for c. Kiriza black.)

X -
- Lamprologus brevis, either pair or group of 6. (is there a different way to have these in numbers?)
- Lamprologus kungweezis, either trio (1m,2f) or group of 6. (is there a different way to have these in numbers?)
- Lamprologus multifasciatus, either trio (1m,2f) or group of 6. (is there a different way to have these in numbers? Would they be best in a pair?)
- Lamprologus ocellatus, either trio (1m,2f) or group of 6. (is there a different way to have these in numbers? Would they be best in a pair?)
- Lamprologus signatus, either trio (1m,2f) or group of 6. (is there a different way to have these in numbers?)
- Any other suggestions for x?

Y -
- Julidochromis dickfeldi, pair (or is a different number better?)
- Julidochromis ornatus, pair (or is a different number better?)
- Julidochromis transcriptus, pair (or is a different number better?)
- Julidochromis transcriptus gombi, pair (or is a different number better?)
-- Telmatochromis bifrenatus, pair (or is a different number better?)
-- Telmatochromis brachygnathus, pair (or is a different number better?)
- Telmatochromis vittatus, pair (or is a different number better?)
- Any other suggestions for y?

Z -
- Cyprichromis microlepidotus, likely black. Is six a good group size?
- Any other suggestions for z?

I believe this one can fit into multiple categories.
XY -
- Lamprologus caudopunktatus r. f., pair (or is a different number better?)
- Lamprologus brichardi, pair (or is a different number better?)
- Lamprologus gracilis, would this be capable of being kept as just one and then possible to either have a group in x and y or a group in x or y? Otherwise, would it be best to be kept in a pair or a group of 6?
-- Telmatochromis brichardi, pair (or is a different number better?)

Not sure about zone -
- Xenotilapia ochrogenys, the information that I managed to find is unsure on which location they would come into, or whether they would prefer something different like a wide open sand land (which will be present in the middle of x and y)

(fish listed with -- and not - are fish that I do not have on the most recent supplier list; however, there is all the chance that I would be able to source them.)

Please tell me if attempting even two different fish is a bad idea. And if anyone has done similar with their tanks, would you mind sharing or showing them? I would love to get some further inspiration!

Open to any ideas.