First off, Sophia unchallenged ends in either of two ways: she and Golitsyn get their way and Russia modernises albeit on a totally different trajectory from Peter's - or the boyars collude with the church and restrain her, leading to Muscovite business as usual, whatever that may be.
Secondly, Russia had reached the Pacific already in Alexei's time. That is not going to change. Sophia's Nerchinsk treaty with China was actually upheld by Peter. In fact, their foreign policy seems to have been hugely similar. Anti-Turk, anti-Swede, anti-Persian. Peace with Qing. Peacetime influence over Poland. She was more pro-Austrian, he was more pro-Dutch, but hey.
Thirdly, if Golitsyn's land reform actually takes place (a big, huge if), you might actually get a lot of free but landless settlers (not wishing to get caught in the landowners' boundary-beating contests) heading out east to farm, fish and collect yasak part-time. Siberia may actually profit, though that's hard to say either way.
And just because Qing could potentially take over the Amur valley, it does not mean they would suddenly develop ocean-going ambitions. On the other hand, Sophia's government is unlikely to be as navy-focused as Peter's, so Russia may never get Alaska at all, or perhaps rely on the promyshelnniki, or perhaps even the Dutch instead.