Though I have only a single mature Fiddle Leaf, she is now 25+ years old. She started out as a spindly, single-stemmed plant and now has eight "trunks." She is in what appears to be a sizable 24" pot, and certainly that is a substantial pot. That being said, this Fiddle has been in the same pot, without refreshing the potting soil, for 10 years. Thus, the questions: "How often do I need to repot my Fiddle Leaf?" and "Does a Fiddle Leaf do well root-bound?" are answered here. That's not to say you need to keep your plant root-bound and/or under-potted. I just wanted to point out that the Fiddle is an incredibly strong plant and can well tolerate situations that many plants could not.
Another pair of questions I get several times each year are: "How can I get my (spindly) Fiddle Leaf to branch?" and "How do I control the size of my Fiddle Leaf?" Keep in mind that the Fiddle is unlike the vast majority of houseplants in that it is a tree in nature, a tree that can get up to 50' tall. Probably the saving grace in growing this tree inside is the fact that it is an evergreen and the fact that it has huge, light-gathering leaves. These trees will naturally branch given time (several years). To speed up this process, one can trim this plant back twice a year. Not only will you encourage branching, but you also will keep the height of the tree within bounds. This is what I do.
Just a side-note here. You might notice that several pictures show wads of sphagnum moss on my Fiddle's limbs. I said I keep my plant compact and control her height/width by trimming. I don't actually do much "trimming," though. I now air-layer her branches, and when the branches have rooted, I cut them and pot them up, creating new, instantly mature plants. I will actually cut six branches today and pot up those air-layered, rooted stems.
Another question asked concerns the asymmetry of the plant: "How can I get my plant to be more uniform in growth?" Part of that answer is the same as the previous answer to the branching question. Judicious trimming will produce (in time) a more symmetrical plant. You need to understand as well the light-needs of this tree. It needs bright, indirect light to do well. If only one side of the plant gets adequate, bright light, that side will always look thicker and have healthier looking leaves, and the branches will always grow towards the light source. To keep symmetry in the tree, rotate the plant 90 degrees every 3-4 months, so that all sides/all leaves receive similar light. I have not rotated my Fiddle since it was put inside in November. Notice that I am growing my tree straddled between a glass-roof area and a wood-ceiling area. You'll see how the half getting less light is somewhat sparse and the leaves are angling towards the better-light. The leaves are also much darker green. Compare that with the side of the plant exposed to the light through the glass. Denser growth, healthier growth, and light-green leaves are the norm here.
The last two pictures show the mother plant after having had six 2' branches removed and those rooted branches potted. She looks a little ragged and is about 2 feet shorter, but in 3-4 months you won't be able to tell she's ever been trimmed.
Fiddle Leaf straddles the solarium light source
Less light exposure
Brighter light exposure
"Trunks" and air-divisions
After "trimming" six 2' branches