Look like you've got some decent suggestions here already for pannier bags but I'd recommend:

-Feed bag instead of a water bottle holder: They can carry anything, not just water bottles, and you can just all sorts of different bottles. Since they're soft fabric, they don't get damage if you bump them hard or something hits them.

-Cameras would definitely be a good idea, I like 360 cameras because you don't have to aim them (I have an insta360 x5, which has replaceable lenses).

-Repair kit, patch kit, and an IFAK are all good things to carry. Might want to pick up some tire levers too, Pedros are good. You'll want a spare tube or two as well as a pump (I like Topeak Morphs).

Adding reflective tape and additional front/rear flashing lights as well as a full face helmet, padded, gloves, and eye protection would also be smart. First aid training, stop the bleed training, and driving school would also be strongly recommended if you don't already have that training.

Ride defensively and assume that nobody can see you when you're riding, drivers can be very dangerous. Also be sure to ride respectfully, don't ride fast on footpaths, dismount or go around if you encounter a crowd, and just don't be an asshole because that's how e-bikes get banned from places.

Good luck and have fun, having an e-bike can be a game changer.

By the way, I featured your post so it will stay at the top for a while and get you more answers.

I've bought random cheap-ish pannier bags of Amazon and had mostly good luck. As long as they're well made (check reviews, inspect pictures - especially user photos) and compatible with your bike, they'll probably be fine. If you want something really good, yeah, Ortlieb is the way to go.

Cameras, lights, and highly visible protective gear are also good ideas. For waterbottle holders I gave up on cages and switched to feedbags after watching some Ryan Van Duzer touring videos: 10/10, would recommend.

Camera wise: I used to have a Contour Roam but that broke, then I got a Ghost XL Drift, but that broke, now I have an Insta360 X5 and it covers all directions on top of my helmet. The X6 would probably be better because it's lower profile but you can buy adapters that will let older 360s lay flat if you want.

For your repair kit include a patch kit, a tube or two, a bike multitool, tire levers, oil if you have a chain, quick links if you have a chain, and a quicklink tool. If you use a belt drive, a spare belt is a good idea.

Cargo rack bag (what is this called?)

Panniers. Way better than a backpack, especially when it's hot.

As for panniers, I'm really happy with the bags I've bought from a Chinese brand called Rhinowalk. Same goes for a saddle bag to contain emergency repair things.

In the saddle bag I have a multitool, an electric pump (I have the one from Coospo, another Chinese brand), a manual pump in case the electric one fails, two spare inner tubes (TPU tubes from RideNow, which as you can guess is a Chinese brand), some tyre levers, and patch kit for the inner tubes.

I use Bushwacker panniers, specifically the Omaha grocery panniers and they're pretty good. Got them used off ebay and they still hold a lot of weight for being probably 10+ years old. My only issue is that with no weight and folded in, the bags will pop off if going over a big bump. But I just use the lower hook tied to the handle so thats never an issue anymore.

https://www.bushwhackerbag.com/products/bicycle-bags/rack-bags-panniers/

For a water bottle holder, I got an Arundel one size fits most. Kinda expensive at 30$ but is useful for wine bottles lol.

https://arundelbike.com/products/looney-bin

I have a Seymour EXP trunk bag which has small, integrated panniers.
This is sitting on my Ortlieb Quick-Rack.

They do what i ask of them. 👌

My repair kit consists of:
multitool, levers, Co2, Co2 adapter, tube.
This setup is geared toward local rides, I would definitely expand it for long rides alone.