pruning for aesthetic purposes ... is a lifetime job ... the life of the tree .. you just start.. and keep at it.. to accomplish your goals ...

understand that trees do not stop growing at some magical height nor width... so dont bank on those labels ...

as to height.. the tag tells you they are not going to be 75 foot oak trees ... so thats a start.. but beyond that .. they will get as tall as they want over the decades ...

as to width .. well.. just about the same ... these arent going to be 50 foot wide shade trees ... but i dont put much faith in a tag that differentiates between 12 feet tall.. as compared to 15 feet.. and same with width ...

just plant one.. learn how to prune for a purpose.. and keep at it.. until it pisses you off and you cut it down.. or move.. lol ... [and then the next owner will find us and we will wonder what you were thinking.. lol...]

i like the primer at the link below on tree planting ...

ken

ps: the hardest variable you have to overcome.. will be watering on a hill .... the proper deep watering a transplanted tree needs to get established and thrive .. its not a sprinkle the surface thing .. you will need to keep moisture down at root level.. until the tree grows a root mass that can cope with your location ...

https://sites.google.com/site/tnarboretum/Home/planting-a-tree-or-shrub

A Mexicola Grande gets 30 feet tall. That tag is either a misprint, or they grafted onto Mini Cado root stock, which is the only dwarf root stock. You can keep an avocado tree low and spreading, but you have to chop it in half when you get to 1 meter tall, and then you keep pinching the tips back every time they grow 18cm or so. You could probably put a soaker hose below the soil surface to keep the water from running down the hill. Most people advise sprinkling over soaker hoses because you get more coverage, though. If you mulch really well, maybe it will hold the soil in place with sprinkling.