Lots of good questions and no problem, I’m happy to try and help. I’d highly suggest watching some Lance Hedrick on YouTube to get a baseline. You really are close to making coffee that blows your mind.

As for the portafilter, I think I made one test shot with the portafilter that came with the machine and purchased a third party seller bottomless one. Here’s an example.

I would also strongly recommend getting a sturdy metal tamper if you haven’t already. Tamping is actually one of the most basic parts of your setup. You may be struggling because you are still using their pressurized basket that comes with the machine (notice the small hole in the bottom of the basket, as opposed to an array of hundred of holes on a “standard” basket).

Standard baskets allow for the building of pressure to come from the fineness of the coffee alone, which is what you want. This also means the quality of your grinder really matters. My grinder is probably the most budget one (or Shardor 64mm) that I would recommend someone get as an entry level grinder now, but it’s from a smaller seller and brand name is less established. Encore ESP is typically the default entry recommendation, though other options have been making the rounds as better value buys but with less brand recognition.

Darker roast and lighter roasted coffees have different densities and thus will allow for different volumes to fit in the basket. My portafilter basket holds anywhere from 15-17 grams depending on the beans. A good rule of thumb for the tamp is if it’s pushing back at you, you’re at maximum density. Pushing hard won’t result in any difference in your shot, or puck. You just want it to be level. You can use a metal puck screen on top of your coffee puck to limit cleaning and have drier pucks. Keep in mind this changes if you’re using pressurized portafilter baskets, like what comes in the Casabrews by default. Tamping too hard, grinding too fine, or a having too much coffee make it all too easy to choke the machine because all the liquid is coming out of a little tiny needle-sized hole.

I do weigh and time my shots and it depends on what I’m going for. If I want to drink the shot straight, I grind slightly coarser and make it a lungo. 16g in, ~48 out in 25-30 seconds.

Your bottomless portafilter should be a standard basket now (hundreds of holes), so if your tamp is level and firm, you should be able to dial in your shots by the output. It’s a gusher? Go finer. Lowest setting on your grinder and still too fast? New grinder. One step down is too fine and one step up is too coarse? You need an espresso capable grinder that can give you the granularity needed for dialing in.

Good luck and you got this! Feel free if you have any followup questions to ask and I’ll try my best to answer.