The Bose Frames are non-polarized sunglasses with special speakers built into each arm. The idea is that they’re designed to look like regular sunglasses, but also act as Bluetooth headphones. Since there’s no earbud that actually goes into your ears, the speakers have been engineered to shoot audio down into your ears; the neat thing is that the Bose Frames do a very good job at masking your audio so that the people around you can’t really hear what you’re listening to. They are available in two different frame styles, round (Rondo) or square (Aldo).
A headset is a headphone combined with a microphone. Headsets provide the equivalent functionality of a telephone handset with hands-free operation. Among applications for headsets, besides telephone use, are aviation, theatre or television studio intercom systems, and console or PC gaming. Headsets are made with either a single-earpiece (mono) or a double-earpiece (mono to both ears or stereo). The microphone arm of headsets is either an external microphone type where the microphone is held in front of the user's mouth, or a voicetube type where the microphone is housed in the earpiece and speech reaches it by means of a hollow tube.
This type combines advantages of earbuds and in-ear headphones – depending on the environment and requirements of the user, they provide passive noise reduction for quality mode (conversation or active music listening) or they give control over the sound environment around user in comfort mode (stand by or background voice/music listening).
I think it’s fair to compare the Grados and HD598, but the M50 is very different and seems not to fit in that comparison. The DT770 is a better comparison to the M50, although the 770 is a better more expensive item. A long time ago I had a Grado 325 and a Sennheiser HD565 – very similar, very enjoyable. Today for that type of sound I might choose the Soundmagic HP100.
The Earbuds 500 won’t be available until early 2020, but they might just be worth waiting for. They look to be the natural successor to the SoundSport Free, the company’s first go at truly wireless earbuds, but probably better in every way. The Earbuds 500 will likely have a longer battery life, a smaller charging case and charge via USB-C. They will be sport-focused, too, and a more affordable option to the company’s other new-age wireless earbuds, the Noise Cancelling Earbuds 700.
Every single Bluetooth codec has significant quality issues—despite many creative solutions employed to make the most of the limited bandwidth the standards employ. For those keeping score at home: not a single codec available can meet wired signal quality. Though Bluetooth audio has come a long way since its noisy beginnings, it’s still not ready to replace the headphone jack. Qualcomm’s aptx HD, and Sony’s LDAC 990kbps codecs come close, but everything else falls far short of the mark.
There are many good articles here on Headfonia. You could click on Buyers’ Guides and read through those, then click on the Headphones topic header for each individual report. The “process” you go through is learning your own sound preferences, then matching that to the products that are available. It is a process, so you have to learn the major differences. Any shortcuts you take might be OK, but when you buy something that you discover you don’t like, make sure you can return that item.