Should i follow a training plan if im not racing till the fall?

My goals are to run a sub-20 min 5k, have an FTP of 3.0 W/kg and swim a sub-30 min 1500m. I don’t necessarily care about racing as much.

Don't worry about things like this. You're not a serious runner so just run as you feel.

Define “serious”. I’m not a good runner but I train a decent amount (12-17 hrs per week) across all disciplines and would like to treat my personal fitness goals seriously.

If you have goals, you need structured training. And how the hell are you training 12-17 hours a week and not breaking 20.

I have a health condition that limits my performance but I can still train.

So I should follow a training plan then to achieve my goals?

To answer the question, yes you should follow some kind of training plan. "Randomly" going out and training doesn't sound super productive. Having a plan holds you accountable, helps motivate you and makes sure you're doing more than just going "easy" every day. Just because you're not competing until the fall, doesn't mean you shouldn't be doing some workouts non-easy days and progressing in your training.

I have no idea what you do during long base phases for triathlon, but for running, I'm mostly doing easy runs, but also strides, relaxed progressions and even a handful of shorter intervals to stay in touch with faster running.

Get a triathlon coach

You stated it yourself you're not interested/serious about racing.

What is your current performance in running swimming and biking at those distances?

How many miles per week are you running?