There is a big difference between 4 inch PVC and 4 inch steel casing. With 4 inch steel casing I would/will opt for an SQ pump with a flow inducer.
If you do use a "4 inch" submersible in 4 inch steel, you would want that pump to be a Slimline/Trimline pump, which is a little smaller. I had my 12-year-old Sta-rite Trimline 4-inch pump reinstalled into my 4 inch steel casing when I got my pit demolished and pitless adapter installed.
The extension can be done different ways. One way is to get a piece made that changes the upper part of the casing to 5-inch. That lets you use a common trapezoidal pitless adapter. Otherwise you would need a thru-way/clear-way pitless adapter.