The machine can be operated without a water filter without any problems. According to the manufacturer's instructions, you can simply omit the filter and use the machine with pre-filtered water.
If you are not using a filter, you can skip the relevant steps in the instructions and use the machine as usual.
Yes, absolutely, in the end you can conjure up a Long Black or Americano with one or two espresso shots and hot water from the milk frother.
Café Creme would be an Americano for me, it's never advisable to make a Café Creme from a portafilter. I prefer the long black version. In the end, both are variants that are diluted with hot water.
I'm very happy with the machine, I've owned it for a year now.