Personally? I'd be looking at what early withdrawals cost, and how often you can do them. If you're putting in 4%, they're putting in 4%, and then an early withdrawal gets hit with a 10% penalty, you're still looking at getting 7.2% instead of the original 4%. Even if you then assume it's taxed at 30% (check your tax bracket of course), you'd still be looking at over 5%, instead of the 4% you're contributing, which you could then walk and buy BTC with.

You can potentially make use of your employer match and buy BTC outside of your plan -- think of it like having your cake and eating it too.

Disclaimer: I'm really not here to suggest you do this. I'm just offering perspective on the math involved IF you're choosing to try to just maximize your bitcoin purchase, as it looks like others are suggesting, and you are considering. What you choose to do in terms of actual investments is nothing I'd want to touch with a 10 foot pole as I'm far from qualified to do so, and even if I were, I'd need a lot more information to build up an appropriate suitability profile. Consult with an investment advisor you trust to find your blind spots and explore your real risk tolerance to fill in your blind spots, and make an educated decision from there. Also, it'd serve you to truly dive deep into what the plan offers. Some currently do offer custodied bitcoin directly (these are rare), and others allow you to have a linked brokerage account that enjoys the plan tax treatment while giving you more flexibility in terms of investment options (these vary heavily based on plans).