How well your last week turns out will make the biggest difference with striations and all that, such as your deletions and loadings. Being dry as a bone will be huge and will make things stand out a lot more.
If you are as you say at a really low body fat already, the degree of your striations at this point is going to have a lot to do with your muscle maturity; i.e. how well that muscle is ingrained in you.
If you are already in the mid to low 4% range with three wks to go, you probably don't need the clen or t-3. You just need to coast and plan out your final week perfectly.
Yes you could use it, and at a low dose as you mentioned...if you get into the mid 3% range it will make a difference, but like I said, that final week is what's most important.
Whatever you do, don't destroy yourself these last few weeks by dropping your calories too much just to get more striations. If you're already really low bf, simply coast and focus on that last week.
