There's lots of info for you to read on the web, but in broad terms, HLG is for broadcast TV i.e. Sky, Virgin, Freeview and Freesat if they ever update their platforms to accommodate High Dynamic Range content.
HDR10 is the core HDR format for streaming/downloads/UHD Blu-ray discs. HDR10+ and Dolby Vision sit on top of the core HDR10 format and add additional benefits. The main advantage is something called Dynamic Metadata. This is the ability to adjust the dynamic range of the TV on a frame-by-frame basis. The benefit is that the set can be adjusted to take full advantage of its entire shade range to suit whatever is being shown.
All this is good in theory, but there are a few important caveats that the salesmen and the manufacturer web sites kind of gloss over.
HDR10+ isn't yet widely adopted, and if it ever gets to be, there may be some subtle differences in LGs implementation compared to Samsong and Panasonic and any other manufacturer that supports the format. That's because its a royalty-free open platform (a big selling point against Dolby Vision), and each manufacturer is capable of interpreting the design parameters to suit themselves.
One of the other big limitations is the TV panel itself. Unless you are buying a mid- to high-end LCD/LED TV or an OLED, then the standard LCD panel found in the bulk of the TVs sold doesn't support the full dynamic range of HDR10 which is 10bit colour. Most LCD TVs are 8 bit panels. That means they support 256 shades of brightness from black to white. (It's actually a bit less than that because we don't use full black or full white in TV or DVD or Blu-ray.) 10bit colour depth is a maximum of 1024 brightness shades. That's four times as many. HDR10 with it's 10bit signal has four shade steps for every single shade step of 8 bit video.
Putting 10-bit panels in to TVs is expensive, so the fudge that the manufacturers use is called dithering. If you're not familiar with the term, it's rapidly alternating a pixel between two colour shaded it can produce to make it look like it's producing a shade in between that's not within the panels capability. The is called 8bit+FRC.
Pulling all this together then and relating it back to your TV choices, they're basic sets. They have 8-bit panels and pseudo-support for simple HDR10. The addition of support for HDR10+ will only really mean something if the format gets off the ground and even then, only if there's content available to make use of it. HDR10+ was announced last January (2018) at CES in Las Vegas. A year on, and despite the involvement of a mastering house capable of encoding this new format, there's still not a lot of HDR10+ material about. DolbyVision is better supported, but you won't generally find that on entry-level sets because of the licencing costs.
Having HDR10+ won't hurt, but it doesn't say anything about the quality of the set or the picture it can produce. Concentrate on buying a decent TV with good basic picture quality first and foremost. With this in mind, the LG 6200 and 6300 have a bit of a problem with brightness. You can read more here:
https://forums.overclockers.co.uk/threads/advice-on-budget-49-lcd-options-400.18845102/https://forums.overclockers.co.uk/threads/advice-on-budget-49-lcd-options-400.18845102/
