The first few days when setting up a new sourdough can be quite inpredictable – but like in your case, there often is an initial burst of activity, followed by a rather quiet phase. This is because during that time, there is no stable “bacterial and yeasty community” yet and one or the other may temporarily prevail. The “not right” smell can also be an indicator of this. This is initial phase of a activity is often interpreted as “the sourdough is ready”, but it is not. And two or three days is really too short for the whole process of creating a new sourdough from scratch.
I suggest you keep feeding your starter for a few more days. Whether you feed once or twice is not crucial, but as long as there is very little activity, once a day should suffice1. There is always the risk of a new starter not working out – if the “wrong” bacteria win over the desired ones – but this will become evident pretty quickly. In this case, discard it, clean your equipment well and start over. And don’t worry, even experienced bakers had new sourdough fail.
۱ Feeding cycles depend a lot on the ratio of starter : (flour & water), in other words, how quickly the yeasts and bacteria “eat up and multiply”.