another tomato plant Q

Tomatoes are very tough plants you can train them how you like. Pinching out the top won't damage the plant but you might not get any flowers/fruit. If you have a couple of trusses below the top then that is all you will get. Pinching out will encourage all the side-shoots to grow and you could encourage those to flower and fruit if you want a bushy plant, but if you have already nipped those out you could end up with a blind plant with no flowers/fruit.