Tolkien planned a Giant in LOTR? + speculations

[Tuor in Gondolin]

I came across this comment in a footnote in
Letters (#35, Feb. 2, 1939)

...though there is no dragon (so far)
there is going to be a Giant"

Of course, he was just beginning the tale (which
clearly continued to grow in the telling) but is anyone
aware of any information about this "Giant", know
of any early writings, or have any speculation about
the giant. It hardly seems to fit Tom Bombadil. Was
he thinking of bringing back Beorn? Could it have
been an early concept of the balrog?

And for sheer speculation...How might LOTR have
evolved if Trotter the Hobbit had not been
replaced by Strider the Dunadain? After all, there
is that tantalizing observation about hobbits going
off, having adventures, and never returning.