No. There is nothing about the big issues in nf that can be activated with exercise, unless you already have pheochromacytoma which is causing hypertension.
No. Many folks with NF1 never have problems from it. I'm very pleased you're going to the gym and I hope you enjoy your new body and your new friendships.
Not usually. Some patients with nf1 have deformities of spine and extremities which may limit physical actiities. If mild form of nf without physical restrictions exercise should not be deleterious. Exercise is good for most individuals.