Not a stupid question! Following what mark12_30 said (and keep in mind as you read this post that I'm no expert), I think it depends on your preference and what your application is. For instance, if you were going to write in Tengwar youself, using English language and Elvish script, I think it makes sense to space the words (after all, spaces are a part of English). Maybe the elvish language would be different - I know not.
From all I've read, the Tengwar alphabet is indeed extremely adaptable and it is very hard to pin down a precise "correct" usage. There are a myriad variants that were used at different times and places by different people; you cannot be entirely accurate whatever you do. Nor would you be inaccurate. My opinion, and please take it as such, is that at some point you have to develop your own style and method of Tengwar-translation.
I know I'm rambling on and getting away from your question. From what you said I'm guessing you're using online generators to translate your text - that's fine, but I highly recommend learning the Tengwar yourself. So much more fun! And unless you get into it deep it's not as difficult as it seems. I can't vouch for the accuracy of the information, but this is my favourite site for learning Tengwar:
Amanye Tenceli, and since it's rather large and confusing,
this is the page I recommend you start at, but do look around!