You are working through Randstad consultancy is under OPT. Make sure that OPT can be extended. OPT extension is done by University, not Randstad. University need to apply USCIS for your OPT extension.

H1B filing: Your current client can file H1B on April 1st. Under current turmoil situation, you might be knowing that H1B minimum Salary should be 130K to apply for H1B, if new bill is passed. We do not know what holds in future about H1B now. So, applying H1B is a risky game. Even if H1B bill is not passed, getting H1B is purely a luck as its based on quota/lottery.

Another thing, if there is a contract between Randstad and your client company, not to hire you directly, you may not be able to join the client, as that violets the contract. Your client might not be willing to hire you directly.

So, all depends on your OPT extension period to change of status. If you have TPS, you can ask your client to file GC rather than H1B.