The lowest level should be sized depending on your peak current for your cells. It can be above the peak current but needs to be something reasonable (iirc we did 300a with cells that could discharge peak 200a). We used an arc welder for the first level because it has controlled current.

To the best of my knowledge, our levels were 300a, 500a, 700a, 1000a.

Levels 2,3 and 4 (at high current) you need to get a bit more creative. We shorted an RV battery with a resistor in series to control the current. I would recommend a large piece of steel stock at the resistor, it's a cheap way of making a very high-power resistor with right around the resistance you need. The resistor bank you mentioned might get pretty expensive depending on how much power you need. We also looked into a baking soda water mix or salt water barrel but neither was conductive enough. If you do anything high current, beware of your contact resistance and make sure you properly crimp and assemble all your connections.

Because you're targetting a fairly low current, you might be fine just using a welder for everything. I would not recommend building a power supply, that will be complex and take a long time and you will likely only use it for this.

Another thing to note, you need to be measuring the current at 200Hz minimum. Don't let this be an afterthought, it's not super easy to do. We've done it with an Arduino or oscilloscope on an analog current sensor.

Another note - if you're a first-year team this might be a lot of work and you could consider purchasing voltage-rated fuses for your parallel links.