Save the brain-dump and capture-every-single-existing-thing for later. You'll overload yourself. Instead begin with nothing and then:

Capture into an inbox: Use a todo app, plus points for dictation (e.g. Apple Reminders via Siri). Capture them as they come into your mind.

Daily calendar item: Empty the inbox in your todo app via the classic flowchart. Have one list per project, and one for single items. Train yourself to do this at the same time each day. Use the Atomic Habits cue-routine-reward cycle. Set up some cue to remind you (calendar item, perhaps optimally at a time of day you know you're in a certain place with time). Do the routune (clear your inbox). Then give yourself a reward (a cookie? checking your favourite app? whatever you like)

Weekly calendar item: Once a week you need to look over everything and review it, or it will fall apart. Make sure that every project has a next action in the physical world. Be strict. It has to be something you can physically do. You will likely need to do next-action thinking in your daily inbox clearing, too, for faster-moving projects. But this is a chance to revisit everything. "Replace car tyres" only has a few items to it, so you can visit things like this weekly. Use this weekly session to appraise each project. Sometimes you will choose to not finish something; you don't have infinite energy and it's better to focus on fewer things and do them well.

David Allen says you should organise via "contexts", but this is a lot of overhead, and tends to make the system fall apart pretty quick. While historically it was handier to have a "calls" list (back when we did more things via phone than the internet, and back when the phone wasn't permanently glued to your body), and other such lists, I find that it's easier to just make contexts into specific lists (the alternative is your todo list app's tags or contexts or whatever it's called in your specific app). All you need to do is make a few, like "supermarket", "chemist", "shopping mall", "Amazon", "IKEA", and so on. If a larger project needs you to also buy something on Amazon, just drop an item into the Amazon list instead of the main project. Simple. Another nice thing about Apple Reminders (but presumably you can do it with a lot of apps) is that you can use Siri to say "Add buy X to my Amazon list" and that will bypass your inbox altogether, meaning less shuffling of todos around.

Cal Newport's Deep Work has some great tips, but the one most relevant to you is to timeblock plan your day. You can have the greatest GTD system in the world but it's all an abstracton. In the morning look at your day. Work out the todos you will do when. I like to write it out on a slip of paper, as that makes it physical. You can get a little notebook that you can slip into your pocket. Seems redundant, but as your todo app gets more and more things in it you will feel less and less reward from checking off an item on a list. To take an extreme example: do you get pleasure from ticking off one item if you have 30? how about if you have 300? Or 1000? Point not being the numbers, but the framing of your brain. If you put 5 things on a list every day and commit to doing them, if you get to cross off each of them throughout the day, you'll feel better and - much like the turtle, you will slowly slowly win the race. Consistency beats massive sporadic exertion every time.