For a mod capable of such high levels, I am going to recommend pretty much the best battery in the business. The Sony VTC5A, not the 5 but the 5A.
It's a 2500 mah battery. What that means is it will give you exactly average battery life with three in your wismec. I believe the wismec is a series box, so at maximum it would be asking 100w per battery. This is still very high, even for the battery I am recommending.
You can get batteries with higher amp ratings but they considerably drop capacity.. and I am taking it, when you ask for long lasting, that you want a battery with decent battery life but also a decent life span itself. Sony batteries are very well made and do last long.
If you want to vape 220 watts max,i can tell you with three sony vtc5a in your rx300, you can vape at 220 watts all day safely. Just make sure to get them from a reputable seller, as sony batteries are often sold as fakes unfortunately.
I don't recommend going to 3000 mah batteries in this case, as they significantly reduce their current draw capacity even if they give you a bit longer runtime before charge. 2500 mah battery i recommended really is the right one for the RX300 to give you decent life and great performance.. it's the one that does everything well overall.
Hope that helps.
PS Samsung 30Q are going to fry a lot quicker than the vtc5a, so it's up to you whether 20% longer battery life or safety is important. The 30Q IS the best 3000 mah battery, it can safely vape at 25 amps maximum, but you'd be asking your battery for more than that once you go over 200 watts.
EDIT : Your mod at max 300 watts will ask 75 watts per battery.I incorrectly thought it was a 3 battery mod, but it's 4. My apologies. If you want the one with maximum capacity that can vape at 300 watts using 4 of them, i recommend the 30Q also as recommended below. My first choice is still the VTC5A if you can handle a tiny bit less run time. PS this is assuming that the RX3000 uses all 4 batteries in series equally split. I have to investigate that to be 100% sure.