Whether to remove branches or not depends on what parts of the tree you intend to use in the final bonsai. many beginners (mistakenly) think they will use the whole trunk of a seedling. More experienced pine growers realize that much of the trunk will be used as sacrifice to thicken the lower trunk and cut off eventually. A great many bonsai pines were developed using the lowest part of the trunk and the lowest branch to grow a new leader.
Some good pines can be developed by bending the lower trunk as
@Thomas J. has shown above but you will usually sacrifice the main trunk and use one of the second whorl of branches for a new leader.
I usually look at the distance between first and second branches to decide whether to chop longer or shorter. If the internode between the 2 is long (relative to the estimated final bonsai height) I'll usually use on of the lower branches as new trunk. Obviously reverse taper in the trunk above that level will not be a problem as it will all be chopped off.
I do not mean to chop now. Chop the sacrifice trunk when the lower trunk has achieved most of the planned thickness which may be 3-8 years. In the meantime manage lowest branches to retain short internodes and good bends that will make a good bonsai after the reduction.
There is a lot of learning and relearning for new pine growers as pines do not behave as many species we are used to.
Good luck with developing this one.