The UA credit card baggage benefits only apply if you buy your ticket with a UA credit card, which doesn't work if you use a credit card that rewards air travel more (Amex personal plat) or use a corporate card.

Being silver does give you better irrops priority but UA IT is really good that it's rare that you need to call in.

Not chasing Marriott titanium seems like a smart path. The question I have is your travel patterns. You need to travel enough to make the annual economy plus subscription worth it but not often enough to qualify for silver.

If your travel patterns are frequent but short and low priced trips, consider the united club card for club access. You can use miles for the annual fee and at 30k points, that's not a bad rate if you use it frequently. You'll get a sign up bonus with the card that essentially funds 2-3 years of annual fees if you meet the spend requirement.

Another alternative to buying an E+ subscription is buying F when it makes sense. On short competitive routes, F buy ups can be as little as $49, and you earn pqp to get you to silver.

Let's say you fly 12 flights a year at $100 pqp each. That's 1200 pqp. At $600/year for a economy plus subscription that's probably the breakeven point of buying it individually. You could buy the subscription or buy E+ individually or F buy ups individually, but let's say that takes you to 1800 pqp. You'll get some starter pqp for being silver this year. That's probably half way to being silver with a conservative travel estimate and you could get another $2000 pqp by spending $40,000 on your new UA card (quest or personal club, the Explorer has a 1000 pqp limit) . If you fly more often or your segment cost is higher that gets you even closer to silver. The e+ subscription might be a stop gap for a year but you can probably make your way to silver for next year and not need the subscription.