To answer your first question

[vivid crow]

Wow thanks very much for the long and detailed response 😄

It sounds like one can use mixture of what lloyd (red iron) said earlier - make some assets yourself, hire an artist to make other assets and use the Unity store for others. To give some background, I'm making a solo project that I'm doing in my free time and there's no time constraint. Thanks again for your help 🙂

[thorn sequoia]

Start focusing on your project's behaviour. Get that working first before you worry about quality and looks. 90% of your game should focus on establishing the fun of your game. The other 10% is just adding a layer of graphics feeling to your game. E.g. story, narrative, guidance, VFX - Things that helps buy player's time and attention towards your game quality, when really they should spend time solving problems and challenges you're trying to introduce to the player.