Do not worry too much about TAP. I have actually in the past chosen TAP over other airlines (AF, Brussel Airlines, BA) if I had to fly Economy long haul on certain routes. The main reason was the (relatively) good leg room in Eco. (But that was on their A340s, maybe you get less room on their - newer - A330s.)

I know they have a bad reputation, but I have never (in about 25 flights) had any really bad experiences with them. (Read: worse than other airlines... ) And OPO is a nice place to connect.

Anyway, I would choose them over KLM any day! (Since that is “your” programme...)