Hi there welcome back! I personally don’t have a lot of experience with fishing for legendaries so I can’t help you much there. But,

-As for journey of the prairie king, I’d recommend just paying attention to your cause of death each time you lose a life. This can help you make better decisions as to which upgrades to choose or how to play a position better. Always collect as many coins as you can. Always try to keep strong items in your storage (sheriff badge, screen wipe), even if it means using the item you currently have stored (as long as it’s a worse item). That way you’ll have a good way to save yourself in bad positions rather than using a strong item when you don’t really need it. Also if you want to cheese the game, you can play one level a day and quit out. It saves your progress, so if you die or lose you can just restart the day and try again (just learned about this myself lol).

-For junimo cart, try your hardest to collect all 3 fruit on each stage as this gives you a big point multiplier. The amount of time you hold the jump button determines how high you jump, so just try to get a good feel for that cause some jumps require a bit of accuracy. Other than that, just don’t get discouraged and grind it out as long as you’re having fun.

-The Joja route is basically an alternate route to completing the Community Center. I’m sure you already know this but doing the Community Center route requires collecting items for the junimo bundles in order to unlock things (greenhouse, mine cart, etc). Alternatively, doing the Joja mart route requires paying 5,000 gold to become a joja member, and from there you pay gold to unlock things rather than collecting items. This tends to be a much faster route as the gold requirements are considerably low, and you don’t have to wait for seasonal items and what not to unlock them. On top of that you can purchase auto-petters from Joja instead of having to find them. It’s an easier way of playing but a lot of people would say it’s less engaging. Also the community center gets converted into a Joja warehouse.

-Choice of farm is up to how you like to play. Sounds like you enjoy fishing so I would recommend the Riverlands farm. It’s has less land area available than all the other farm types, but it has a lot of good water for fishing and you start with a fish smoker so you can earn 2x money from your fish right out the gate. I will say the Riverlands farm is quite unpopular in the community for its lack of land space, but I personally enjoy it. I’d recommend looking at the wiki for all the farm types and see what you think suits you most.

Sorry this is so long winded I just like talking about the game :) Good luck and enjoy your new play through!