Of course you must test them. Performing is the most important. Every manager of course has his one way playing, his target and goals.
In my case, knowing that those players aren't fast trainers, I would be very demanding. Meaning that I would expect not only good rates but some goals as well. Because that's the job of a striker
Let me sow you my STs
My main ST, NEYMAR, a fast trainer I bought 6-7 seasons ago (and gave him sa one-to-one). What can I say for him. Just saving greens to make him last as he can
My second ST, ADEMIR. A fast trainer I bought this season and also gave him one-to-one sa. He looks promising, having good stats as goals also.
BEBETO, a second class nordgen, not so fast. He had good rates but he doesn't scores much. I have him as a replacement of NEYMAR in easy games. I 'm gonna sell him by the end of the season.
ZARDEL, same case (an ex- scout list player). Good rates but not enough goals. Same as BEBETO, a sub. Gonna sell him too in the end of the season.
So, it depends from your target, strategy and what else you have at that time.
So test them , train them but don't give them sp and make them 6* players so you can sell them easy if you want later.
* test them in official games. Friendly games don't give you reliable conclusions.
**Don't take it for granted.... I want to keep him because of his Attacking attributes
As you can see, I prefer to give skill points to my ST, mostly to attack and M&P ,but this doesn't make every ST better.
ADEMIR for example has more balanced skills than ZARDEL or BEBETO but he is a better scorer.