Got a second hand FT-857 last week, you can’t tell from the printed label whether it is a FT-857 or the D or the ND version, and also there are options like a TCXO and various filters. This one seems to be the D version because it has 60m and it has DSP filtering, and the CW filter is clearly there although I probably won’t use it. The receiver performs like a charm, maybe it seems somewhat noisier than the FT-991 but, if you play around with the RF gain and the filters, and if you listen on the headset then it is a very acceptable transceiver. No ATU, so your antenna SWR needs to be under 3 (probably), but to be honest, it is not very difficult to tune the antenna with a separate analyzer. Already did this for the vertical whip for 20m so I took the FT-857 in the field and made some QSOs.
I like this set-up for in the car, it is easy to do, easier compared to getting the FT-991 in the field. The 857 fits on your dashboard, everything (cables headset, mike, ropes) fits in one suitcase, with the 991 I end up carrying at least a bag next to the suitcase. Getting my tuner to work with this set still needs some work, the LDG YT-1200 is designed for the CAT interface, and not a CAT-IV interface, so I need a conversion cable and some conversion electronics.
The challenge is, arrange yourself in such a way that you can hike for several km, carry a GFK mast, a 100 Watt transceiver, batteries, cables, tuner, and all antenna material without the help of anyone. Today I came close to this, I had a suitcase and a separate bag, and a mast attached to a tripod. It is not comfortable hiking, but it worked.