A NAS is network attached storage. It generally refers to an appliance that can host from 1-6 disks, is easy to setup and manage and generally has 1-2 USB2 and these days 1-2 USB3 ports for external storage to be hooked up. Its fast and easy setup to get your storage on your network.
If you want wireless access, attach the NAS to your router through a network cable and now you can access it through wired and wireless clients.
For performance, YMMV.
What adapters are they, what routers are we talking, what kind of construction is your domicile, what kind of neighboring wireless networks do you have.
What kind of tablet is it? Since tablet and 11ac, I am assuming it is a 1:1 adapter. With a decent 11ac router, over wireless I'd expect you to probably cap out around 20MB/sec at best. Depending on the storage system on the tablet, it might be slower than that (most tablets have very slow eMMC storage). A lot of wireless adapters in tablets are also connected over the SDIO bus, which is limited to 100Mbps, so even if the adapter could do faster, you are looking at a hard and fast limit of around 80-90Mbps realistically (or around 10-11MB/sec).
Phone, figure slower.
Laptop, can it do 5GHz? Is it a 1:1? 2:2? 3:3? Results will vary. A 2.4GHz 1:1 adapter with 20MHz channel width is probably only going to hit 30Mbps or 3.5MB/sec with a tail wind. Worse if you have a lot of neighboring networks. With a really nice 3:3 adapter on 5GHz same room and an excellent router than can support 3:3 you might get 300Mbps or 35MB/sec.
Same room mind you.
I have an AWESOME setup for wireless. I can get around 20-25MB/sec to my laptop on 2.4GHz depending on if it is my router or AP I am connecting to (if both are set to 40MHz, which I don't actually do with both) same room. Move around a little and it drops a bit, but the worst place in my house on 2.4GHz if I set 40MHz channel widths with my laptop is around 15MB/sec. The way I normally have it setup for 20MHz on my router and 40MHz on my AP means realistically the worst performance is around 9MB/sec on 2.4GHz on my laptop. 5GHz performance varies a lot more as my router is an AC1750 and my AP is an N600. Same room with the AP it is 25MB/sec, one room over it drops to 10-15MB/sec (I have a big old chimney in the way). With my router it can be >50MB/sec same room, move a room away and it is still generally over 40MB/sec. Move a couple of rooms over and we are talking mid-high 20's, much further and I lose 5GHz connection entirely.
On my tablet which is N300 (2.4/5GHz, so just 150Mbps each) it can do around 10MB/sec on 2.4GHz 40MHz and a little slower on 5GHz 40MHz (about 9.5MB/sec). I get those kinds of speeds over most of my house, but the worst performance is down around 5MB/sec when connected in the worst location on 2.4GHz 20MHz. Phone is a little slower at around 3-6MB/sec depending on where I am connected in my house.
If I bother to wire my laptop in I get ~114MB/sec both ways at the same time to my file server. If I sit at my desktop I get ~235MB/sec both ways at the same time from dual NICs and SMB multichannel (sigh, if only my disk array could actually support that performance though, its unidirectional ~235MB/sec, otherwise performance falls off a cliff if trying to do reads and writes at full speed, about 100-140MB/sec read AND write concurrently with big sequential transfers, don't ask on small I/O, they are spinning disks).
For options, look at the features of other routers. Its called research. Some do support download/torrent servers on their routers. Not a lot, but a few others do. All Synology and QNAP NAS have download/torrent servers to the best of my knowledge. As well as a lot of other features.
