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I think what I was asking originally is platform-specific, but I guess it doesn't surprise me that Apple doesn't really have "entry level" hardware, at least nothing like Roku or Amazon's 30-50$ options. What I was asking specific was - for example - what is the meaningful difference between FireStick and FireTV cube. I don't consider 4k here since in most cases it's probably an artificial restriction and is a fairly binary choice - you either need 4k or you don't.
To take your question literally, the main difference between the Fire Stick and the Fire TV Cube is that the Cube has Alexa built-in with a microphone so you can talk to it without using the remote. That is, the Fire Stick has an Alexa-enabled remote where you hold down the microphone button and then tell it what you want it to do. With the Cube, you don't need to use the remote to do that—so, in theory, you could say, "Alexa, open Acorn TV" and it will launch that service. You can also ask the Cube most of the usual things you might ask an Alexa-enabled device—"Alexa, what was the score of yesterday's Nationals game?" or "Alexa, turn on the bedroom lights." The Fire Stick can't do those things.
The voice control is unreliable, though (and this is true for the Stick as well as the Cube). It doesn't work with all services (I can't make it work with YouTube TV on either the Amazon devices or the Apple TV), and it sometimes confuses channel names due to similarity (NBC Sports Washington, NBC Sports Network, and NBC all seem to confuse it as to which I want). The other thing is, the Cube can be a problem because by its nature it's placed near your TV, which means if you have the built-in microphone turned on, Amazon commercials, and for that matter any other word on TV that sounds like "Alexa," can wake it up. When that happens, it mutes the TV as it acknowledges your request and then tries to do what you want. Thus, at a minimum you want to make sure to adjust the security so the Cube cannot order anything from Amazon without you providing a PIN. I simply turned off voice-ordering. Ultimately, I wound up just muting the Cube's microphone because I didn't like it muting the TV at random, so I just use the microphone on the remote when I want to control it by voice. (I got the Cube at 50% off when it was on sale. I think if I were paying full price I'd likely go for another Apple TV instead.)
I have not yet confirmed whether or how well the Fire devices do with a VPN or DNS service like Unlocator. I'm told location-spoofing may be more difficult with those than it is with an Apple TV, but I just haven't tried it yet.
Regarding Apple TV, you may find used devices available at a discount, but be wary of those. The older devices didn't support downloading TV apps the way the current generation does, so that impairs their usefulness.