No, you don't miss much not doing the two boring days on the slow boat;
there are better boat trips anyway.
No, you won't miss much not going to LNT and trek overnight to village
there; you can do that in many other places in Laos.
Like trains? Train Bkk-Vinetiane
Then Vang-Vieng-Luang Prabang-boat trip Nam Ou to Nong Khiaw - Muang
Ngoi-back to Nong Khiaw-Xam Neua-Phonsavanh -direct to Pakxan (buses dry season
only)-ViengKham-Nahin/Khonglor-Thakek-Savn'ket-Pakse-Champasak-4000islands;
then back into Thailand, by bus to Ubon Ratch, by train back to Bangkok.
Gets you away from the pancake trail a bit.
Trekking: out of Nong Khiaw, Khonglor, Pakse.
However rather a full month itenary and not 20-21 days.Options to speed up things:
Skip Vang Vieng (you will see more stunning carst peak at Khonglor), Muang Ngoi (little Vang Vieng hang loose community, carst scenery again); on the way to Pakse one stop (or do no stop) overnight is enought o break the journey, no need to do both Thakhek and S'keth.
That would be ok in about 21 days.
