I would never buy the US consumer junk that's out there. I have only ever purchased my equipment from a Dahua dealer, who drop ships everything 2-day air from Hong Kong. If you've heard the name before on IPCamTalk or elsewhere, I sourced my equipment through Andy at EmpireTech. The equipment I bought cannot be purchased in the US under Dahua or any other Brand name, though with that said Andy actually has a handful of items listed on Amazon lol. So the only reason I haven't tried out any Hik equipment is because I do not have a Hik rep to buy the equipment from. Buying from some random dealer online or from Alibaba is like playing Russian roulette with 6 in the barrel. I'd sooner light my cash on fire so I can at least say I did something baller with it.Dahua gear is generally pretty reliable, but I really don't like their cameras, they suck. I've done several side by side comparisons over the years of Dahua vs. Hikvision, Speco and a few other brands and Dahua is always worse in picture quality in lower light levels, especially at night when using IR.
1) You are indeed correct the UI on these lower tier units is trash, it's a constant headache. Hikvision had a big UI update a couple of years ago which completely scrambled everything in an attempt to modernize the look, which had function as an afterthought. I still think they offer the best value though, which is why I put up with them.
If you're looking for a good user experience and support, Axis is probably the best out there, but you pay for it. Axis cameras are very expensive, but the UI is amazing and they have really good support. I've only ever installed a few of them, but they were a breeze to configure compared to any other vendor, and the video quality is really good.
2) This is true if you get the low end consumer trash they sell at retail stores, but not with better quality units generally only available to installers. I have used Hikvision TurboHD DVRs with different brand cameras, because they're compatible with CVBS, CVI, HDI and AHD. Likewise with Hikvision NVRs because it supports any camera that has ONVIF support. The reason why you hear that different brand cameras don't work on consumer gear is because the consumer space is flooded with shitty fly by night vendors who spec equipment from one of the big camera vendors like Hikvision, Dahua, Speco and a couple of others. They'll get cut-down equipment made for them with their label that usually has a locked FW on the DVR/NVR and sometimes cameras so that you can only use their gear.
One such example was Lorex, which used Hikvision gear for a long time and then switched everything over to Dahua. Nothing was compatible between them because they had a locked firmware on their NVRs. There was a way to hack the older NVRs to take an official Hikvision firmware and enable ONVIF support, but it was a long and complicated process.
I never advise my customers to buy the trash available at retail stores because of issues like that, and there's a high chance the company won't be around for more than a year. The companies that sell that crap cycle around all the time and you're basically guaranteed to not have support in the future. Unfortunately, they're never going to go away because they're so cheap and people are going to keep getting burned.
3) Yeah, that's how my customers got into the PC DVR mess. They make it sound like its cheaper and easier, but it really isn't.
Milestone does have a decent learning curve. I would honestly get an 8 channel Hikvision, Speco or even DW NVR and call it a day. You can probably see I'm partial to Hikvision, but Speco and DW are also pretty good.
From my understanding, virtually all IP cams are made by either Dahua or Hikvision, including Axis cams. I don't know what you consider expensive, but my cams ran between $150-180/cam, depending on model. The starlight cams are known for being very very good in low-light settings, which is why I bought them. The ones at the rental property are excellent in low-light (Dahua IPC-HDW5231R-Z). The newer version of the same cam I got for my house now doesn't perform as well in low light (Dahua IPC-HDW5231R-ZE). This is color low light FYI, no IR on at all. My older Starlights make it look like it's daytime out when it's the dead of night...it's the craziest thing ever. This is much preferred to using IR IMO.
The NVR I'm running at the rental was $330 if I remember correctly. It's 4k PoE on all 16 channels (Dahua NVR5216-16P-4KS2). It's got all kinds of crazy features that I'll never use. I know some of the newer NVRs offer dual IP/BNC connections, which is a cool feature if you have old analog cams.
I got into the PC-NVR game knowing I was going to spend more money than if I'd gone with an NVR. It wasn't about the money for me; it was about the ease of use and flexibility. I didn't need to drop well over $2k on a PC-NVR rig, but I purchase a new computer maybe once a decade, so I didn't see it as that big of deal. PLus, now it's serving multiple purposes, including being a Plex server and my current Covid-Workstation lol.