Why

Your "Inquiry volume: 10–50" and "Team size: 2–3" understate the real workload — the unit isn't an inquiry, it's a rep visit, and you're describing 7 distinct activities (visit log, result, calendar, route, notes, photos, ERP lookup) that no lead-pipeline CRM does well out of the box. You already have a capable IT department and a preference for open-source, which rules in self-hosted options that most small businesses can't run. Your real integration question is ERP ↔ visit log, not channel ↔ inbox.

What you actually need

1. Odoo Community Edition (free, self-hosted) — install the CRM + Field Service + Contacts modules. Field Service gives you visit scheduling, on-site notes, photo uploads from the mobile app, and per-client history. Your IT team can run it on a single VPS in an afternoon.
2. Odoo's REST API → your ERP — a read-only sync that pulls client master data (account, address, products bought) into the Contact record so reps see ERP info without leaving the app. One-time job for your IT team, maybe two days.
3. A habit — Friday 30-minute route plan — every Friday afternoon each rep books next week's visits in the Odoo calendar with a one-line objective per stop ("show new sandalwood line", "re-educate on burner safety"). No visit goes on the calendar without an objective.

Do this today

On a spare server or laptop, run `docker run -p 8069:8069 --name odoo -d odoo:17` to spin up Odoo Community, then in Apps install CRM, Field Service, and Contacts. Create one pipeline stage set: Scheduled → Visited → Follow-up Needed → Closed, and import 20 of your top B2B accounts as Contacts. By tonight one rep can install the Odoo mobile app, log a visit with a shop photo, and you'll know if the workflow fits before involving IT on the ERP sync.

What to ignore

Skip Salesforce Field Service (~$165/user/mo), HubSpot Sales Hub Professional, and SAP's field-sales add-ons — all are massively over-priced for 2-3 reps and lock you into proprietary mobile apps. Also skip SuiteCRM and Vtiger for this specific use case: their field-visit modules are weaker than Odoo's, and you'd be patching gaps your IT team shouldn't have to patch.

What doing nothing costs you

With 2-3 reps and no shared visit log, you're paying for trips whose outcomes live only in someone's head — a rep leaves and the relationship history leaves with them. The compounding loss is institutional memory of which shop wants which incense line, which is the entire moat of a specialty B2B distributor.

When to revisit this

When you hire a fourth rep or open a second region where route planning stops being doable on a paper map.