Is it really correct to say that Biden vs trump won’t have an affect on those at the bottom? Even if it’s slight? There’s at least some emphasis on free healthcare, raising minimum wage amongst the dems right?

Here's a little tip: when you start talking in terms of "emphasis", "centering", "focusing", you're not talking about politics anymore, you're talking about branding. "Free healthcare" and wage increases are ideas that are merely associated with the Democratic brand right now, as abortion and immigration restriction are associated with the Republican brand. These are not commitments, these are not party line items, these ideas are brands in themselves, usually with a slew of NGOs and non-profits to speak on behalf of whatever "cause" they claim to represent. It's all middle-class makework programs masquerading as politics.

You have to understand that the political sphere isn't just a marketplace where two rival products (Democrats & Republicans) compete with one another to win over buyers (voters), thats the neoliberal ideology obfuscating the political. It is a duopoly, an implicit agreement of cooperation between the 2 dominant forces where no other competition is feasible.

You also have to understand that the class composition of both party's donor bases are fundamentally the same, they just represent different factions of the ruling class. Often, both parties are supported by the same people (see: billionaires who donate handsomely to Democratic and Relublican candidates in the same races).

In the case of a political system that is run as a duopoly between 2 parties, every policy or law that does pass is basically a matter of consensus, the feuding and bickering over details is largely just political theater ("politics is showbiz for ugly people").

Democrats get the ACA passed, Republicans get tax cuts, all any of this means is that the ruling classes determined that these measures were appropriate for whatever reason, and leave it up to the party apparatchiks to manufacture the conflict to maintain the illusion of political struggle between 2 fundamentally opposed sides.

The bottom line though is that both parties are equally complicit in the fucking over of the underclass, whoever that is comprised of. Neither party will ever do anything to critically undermine the other, or else the stable and balanced system of power falls apart. If you do see that happen, and not from the influence of a communist party, you might have what is called a "bourgeois revolution", where the shape of the power structure might reconfigure, but only in a way that maintains the dominance of the bourgoisie over the exploited class.