I have had backup cams on every vehicle I've owned for about 10 years and no one has ever tried to steal one. First thing, it's wired into the car, second they're cheap and of little resale value so risk/reward/time combination is fairly poor. My experience is they're going after the radio far more often. Experience being I used to run an install bay and have had several customers come in with stolen amps and radios and never once a camera. Worked in a high crime area as well. The roof of our store was cut into mission impossible style on one occasion.
My camera bracket is behind the license plate and screwed in with temper resistant stainless screws. It requires a bit of effort to get the plate off for the average joe and the wiring I have secured inside the shell of the hatch and used adhesive mounts with zip ties in several places to essentially lock the wire in place should someone or a rouge car wash manage to tear something off so that it would minimize damage to interior wiring and likely just rip the camera body off its wire before causing any other issues. Its small and doesnt draw much attention. Pic attached showing it mocked up before securing everything and changing rhe mounting hardware.
As far as recommendations are there any specifics you're after aside from a screen and backup camera input? You mention an alpine radio and a larger screen wanted but what size do you have now? Typical radios will be in the 6.8-7" range unless you vetting into the floating display types then the sky or rather your wallet is the limit.
I have a Pioneer NEX4500 in my 2003 and it's a 6.95" display which works just fine for basically everything. Wireless android auto, carplay, etc. It's older and not made anymore but has everything the new models do aside from alexa which I have 0 desire for. The wife's navigator I went with the 9" Pioneer WT7600NEX. The screen is massive in comparison to the 4300. On maps its kind if nice to have the larger display as the detail/festures stand out much more. The 720p resolution is also welcome. The backup camera which is identical to mine looks worse, likely due to it being 480 and being scaled to that screen resolution. Other than a better GUI and the larger capacitive display/720p it's basically the same thing and was about $500 more but it fit the look of the truck better and she has terrible eyes, wears glasses obviously but anything to help is always nice.
The newer versions of these, the W4600NEX and the WT76NEX, and if you want 10" the WT8600NEX are great choices and have everything you mentioned and then some. I don't use it often but having miracast and an HDMI input are fantastic. Probably less useful since you're an iPhone user but they've come in handy for me and if you had a laptop being able to have a second screen if you happen to do any work in the field is nice. I've used the navigator screen to keep myself occupied while waiting on our daughter to finish cheer practice a couple times with some xbox remote play with my phone wired hdmi to the 9" screen and the stereo handling the sound. Draws some looks in the parking lot for sure when they hear the gunfire or you yelling at someone in game. Lol. Its equally relaxing with some flight sim too however.