Yes, for exactly one kind of rate: one Soco can't see. Soco only knows the standard commission shown in TikTok Shop, so a deal you made privately with a brand looks like a standard-rate product to Add All to Showcase, and it can be replaced with the standard link. Every other product is safe: Soco only ever adds links with the same or higher commission.
The two cases where Soco can't see your rate
Both come down to your rate not being the standard TikTok Shop commission:
A private or direct brand deal: it never appears as the standard commission, so Soco can't compare against it.
A raise that came after you added the link: Soco checks rates only when you add a link, not continuously, so a later increase is invisible to it.
In both cases Soco sees only the standard rate and may replace your better link. Keep your own link on those products.
Protect a private rate
Skip Add All for those products and add your other links individually instead. There's nothing else to configure; leaving the product out is the protection.
Restore a link Add All already replaced
You can switch back right away. In TikTok, add the brand's own link to that product again: TikTok allows only one affiliate link per product, so your new link replaces the Soco link automatically. The step-by-step version, including what happens to videos you already posted: How do I switch a product back to a higher commission link?
Next steps
The wider mechanics: