As well as filling in your profile, it's a really good idea to also pin an introduction post about yourself to your profile.
Pinned posts let you write a lot more than profile texts, and let you attach photos, audio or video. You can even reply to your own pinned post to create a pinned thread.
More info including how to pin posts:
https://fedi.tips/how-do-i-pin-my-posts-on-my-mastodon-profile
For technical reasons, pinned posts and pinned threads are distributed much more widely than ordinary posts.
I think Friendica supports pinned posts, but @hypolite would be able to confirm that.
On the other issue about the links, really interesting to hear how TweeseCake behaves.
Long links are displayed in a shortened version so that they are easier to read for sighted people, but the actual full links are supposed to be there in the code of the post, so that when people click on them the link opens.
Are you unable to open these links in TweeseCake?
Very long links can feel a bit distracting to sighted readers, that's why they are displayed in a shortened form. This causes the problem that if you copy-paste the post the links get broken.
The character limit isn't an issue, at least on Mastodon, because all links count as 23 characters no matter how long they really are.
Don't worry, please do keep giving feedback if there is a problem!
Especially keen to hear about any problems from screen reader users, as sighted developers sometimes overlook audio users.