It is a common misconception that HMO plans are the only type of plans that cover routine care such as wellness checkups and preventative services. That is generally no longer the case. Since the advent of the Affordable Care Act (ACA), all ACA-compliant plans including Preferred Provider Organization (PPO), Point of Service (POS) plans , etc. are required to offer coverage for physicals and preventive services as part of the law's Minimum Essential Coverage (MEC) requirement.
It is true that the monthly premiums and out-of-pocket costs for additional physician visits and lab tests can sometimes be lower with HMO's than other types of plans with larger provider networks.
HMO's also do require an insured to select a primary care physician (PCP), who would be responsible for all of the routine medical care and referring the insured, if necessary, to any specialty care doctors. Keep in mind that there will be little to no coverage offered for medical services provided by physicians and hospitals outside of the HMO, other than for emergency care.