According to Houston whispers, the Texans won't pursue a new candidate this year. O'Brien will be the GM for 2019. If that's true, I think Caserio will end up in there .... just not in 2019. (His contract will expire next year in Boston.)
Well, Sanders played mostly close to the box, and was covering the middle area of the field a lot in Dungy's system, and Moore plays in the slot, and he is also covering the middle area of the field as well. So, I kinda see why you saw some similarities. However, they are very different types of players, they play at different positions, so there is hardly any similarity if you break down what they do actually. It might seem a bit similar, but it's very different.
And, as others said, Bob was a generational talent. He played on an entirely different level. Remember when teams use to ran 200 / 300 yards against the Colts D in 2006? The entire regular season? Then Bob came back for the playoffs and the Colts D suddenly turned into the big wall of china. That was Sanders, alone. He was a game changer when healthy.
You were correct with your 6 games statement. ;) Only, that 6 games can be gained by being on active roster (which is not game day roster!) or on IR.
(Might worth to add, that players on IR don't count against the 53, but they are under "normal" NFL contract. They can rehab in the team facilities, they can take part in meetings, etc. Please also note, that waiving a player with injury settlement and putting someone on IR are two different move. The latter is the "real" IR. It keeps the player under contract, and be part of the team. The former is practically a cut, with some financial implications. E.g., the team is willing to pay money for the player, if he won't be claimed by another team.)
Regarding Cox, 2017 didn't count as accrued season for him, because he spent most of the year on PS, which does not count. (He wasn't on IR neither. I mean, "under contract" IR, because players can be waived with IR settlement as well, which does not count as accrued season.) Cox will be an ERFA in 2020, and an RFA in 2021.