well as far as I know there aren't any missables.
That's why I usually just play the story and then do side missions, collectables and random stuff afterwards.
I *could* get them all but that would require too much time. Finish 65 Abstergo challenges to unlock a cheat that's necessary for the "Supplier" achievement for example. I was happy when I hit 55 challenges to do some of the other achievements.
Basically I just started looting my first supply camp yesterday, so I have 19 more to loot. That's probably the last achievement I'm going for.

Most of the 16 was just mainly story missions besides a couple I think like reverse boarding and breaking ice sheets. Which 4 are you missing? Is one of them the 100% Sync one? I was thinking of playing 1 more time after and trying different things like fully upgrade the ship as much as possible while being Assassin. But if I do I'd have to leave a few achievements locked to make a 3rd playthrough worthwhile.

It's fine, not like Shay falls off the ground and whatver else bugs Unity had lol. Day one patch was roughly 4 mb's. And I've only seen just that one patch.

Just looked and there are actually 6 I'm missing

One of them is indeed 100% sync. I never do them in AC games.
Looting 20 supply camps as mentioned
Getting the templar armor (collecting 24 maps and then dig out 24 relicts; sounds like that needs a lot of time)
Loot 20 ship convoys (did 3 as part of simply playing the game, don't feel like boarding 17 more frigates)
and last but not least collecting all Animus fragments (From what I remember there are ~250, I have 50 by just playing the game)

I'll try to 100% it on Rogue. I managed to be able to do it on BF even though a couple of sequences did take awhile. I don't see no loot 20 ship convoys unlocked on mine. Is that those ships with those naval chests and a timer pops up when you get in it?

No still trying to get Xbox One the one I bought my relatives took mine and said buy a new one and I cannot right now

Ac rogue is good however voice acting is terrible and mission structure is bit repetitive

No you got it wrong the time I bought mine I had few relatives at my place they said this looks cool can we take it I was confused however they bought me a new pc 1.5 years back so I was helpless and could not deny. Now they own it, I barely played it. Now I need to wait a bit more till the time I buy a new one for me. Can't you fund my purchase without the kidney will love to get Xbox One as a gift but kidney as a return gift. ummmmmmm

Good rewards but now we need Halo reach aswell =p

Well add Halo wars as well and then we have a complete halo package xD